[EE] Add `null: true` to timestamps in migrations that does not define it

This is to ensure that migrations will still be consitent when we will
upgrade to Rails 5 which default to `null: false` for timestamps
columns.

Fixes #23666.
Signed-off-by: Rémy Coutable <remy@rymai.me>

db/migrate/20130319214458_create_forked_project_links.rb

 # rubocop:disable all
 class CreateForkedProjectLinks < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :forked_project_links do |t|
       t.integer :forked_to_project_id, null: false
       t.integer :forked_from_project_id, null: false
 
-      t.timestamps
+      t.timestamps null: true
     end
     add_index :forked_project_links, :forked_to_project_id, unique: true
   end

db/migrate/20130506090604_create_deploy_keys_projects.rb

 # rubocop:disable all
 class CreateDeployKeysProjects < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :deploy_keys_projects do |t|
       t.integer :deploy_key_id, null: false
       t.integer :project_id, null: false
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20130617095603_create_users_groups.rb

 # rubocop:disable all
 class CreateUsersGroups < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :users_groups do |t|
       t.integer :group_access, null: false
       t.integer :group_id, null: false
       t.integer :user_id, null: false
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20130711063759_create_project_group_links.rb

 # rubocop:disable all
 class CreateProjectGroupLinks < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :project_group_links do |t|
       t.integer :project_id, null: false
       t.integer :group_id, null: false
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20131112114325_create_broadcast_messages.rb

 # rubocop:disable all
 class CreateBroadcastMessages < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :broadcast_messages do |t|
       t.text :message, null: false
@@ -7,7 +9,7 @@ class CreateBroadcastMessages < ActiveRecord::Migration
       t.datetime :ends_at
       t.integer :alert_type
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20140122112253_create_merge_request_diffs.rb

 # rubocop:disable all
 class CreateMergeRequestDiffs < ActiveRecord::Migration
+  DOWNTIME = false
+
   def up
     create_table :merge_request_diffs do |t|
       t.string :state, null: false, default: 'collected'
@@ -7,7 +9,7 @@ class CreateMergeRequestDiffs < ActiveRecord::Migration
       t.text :st_diffs, null: true
       t.integer :merge_request_id, null: false
 
-      t.timestamps
+      t.timestamps null: true
     end
 
     if ActiveRecord::Base.configurations[Rails.env]['adapter'] =~ /^mysql/

db/migrate/20140209025651_create_emails.rb

 # rubocop:disable all
 class CreateEmails < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :emails do |t|
       t.integer  :user_id, null: false
       t.string   :email, null: false
-      
-      t.timestamps
+
+      t.timestamps null: true
     end
 
     add_index :emails, :user_id

db/migrate/20140319135450_create_git_hooks.rb

 class CreateGitHooks < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :git_hooks do |t|
       t.string :force_push_regex
@@ -7,7 +9,7 @@ class CreateGitHooks < ActiveRecord::Migration
       t.boolean :deny_delete_tag
       t.integer :project_id
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20140414093351_create_appearances.rb

 class CreateAppearances < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     # GitLab CE may already have created this table, so to preserve
     # the upgrade path from CE -> EE we only create this if necessary.
@@ -9,7 +11,7 @@ class CreateAppearances < ActiveRecord::Migration
         t.string :logo
         t.integer :updated_by
 
-        t.timestamps
+        t.timestamps null: true
       end
     end
   end

db/migrate/20140625115202_create_users_star_projects.rb

 # rubocop:disable all
 class CreateUsersStarProjects < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :users_star_projects do |t|
       t.integer :project_id, null: false
       t.integer :user_id, null: false
-      t.timestamps
+      t.timestamps null: true
     end
     add_index :users_star_projects, :user_id
     add_index :users_star_projects, :project_id

db/migrate/20140729134820_create_labels.rb

 # rubocop:disable all
 class CreateLabels < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :labels do |t|
       t.string :title
       t.string :color
       t.integer :project_id
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20140729140420_create_label_links.rb

 # rubocop:disable all
 class CreateLabelLinks < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :label_links do |t|
       t.integer :label_id
       t.integer :target_id
       t.string :target_type
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20140813090117_add_ldap_groups_table.rb

 class AddLdapGroupsTable < ActiveRecord::Migration
+  DOWNTIME = false
+
   def up
     create_table :ldap_groups do |t|
       t.string :cn, null: false
       t.integer :group_access, null: false
       t.references :group, null: false
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 

db/migrate/20140914113604_add_members_table.rb

 # rubocop:disable all
 class AddMembersTable < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :members do |t|
       t.integer :access_level, null: false
@@ -9,7 +11,7 @@ class AddMembersTable < ActiveRecord::Migration
       t.integer :notification_level, null: false
       t.string  :type
 
-      t.timestamps
+      t.timestamps null: true
     end
 
     add_index :members, :type

db/migrate/20140914173417_remove_old_member_tables.rb

 # rubocop:disable all
 class RemoveOldMemberTables < ActiveRecord::Migration
+  DOWNTIME = false
+
   def up
     drop_table :users_groups
     drop_table :users_projects
@@ -12,7 +14,7 @@ class RemoveOldMemberTables < ActiveRecord::Migration
       t.integer :user_id, null: false
       t.integer :notification_level, null: false, default: 3
 
-      t.timestamps
+      t.timestamps null: true
     end
 
     create_table :users_projects do |t|
@@ -21,7 +23,7 @@ class RemoveOldMemberTables < ActiveRecord::Migration
       t.integer :user_id, null: false
       t.integer :notification_level, null: false, default: 3
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20141118150935_add_audit_event.rb

 # rubocop:disable all
 class AddAuditEvent < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :audit_events do |t|
       t.integer :author_id, null: false
@@ -13,7 +15,7 @@ class AddAuditEvent < ActiveRecord::Migration
       # Details for the event
       t.text  :details
 
-      t.timestamps
+      t.timestamps null: true
     end
 
     add_index :audit_events, :author_id

db/migrate/20141216155758_create_doorkeeper_tables.rb

 # rubocop:disable all
 class CreateDoorkeeperTables < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :oauth_applications do |t|
       t.string  :name,         null: false
@@ -7,7 +9,7 @@ class CreateDoorkeeperTables < ActiveRecord::Migration
       t.string  :secret,       null: false
       t.text    :redirect_uri, null: false
       t.string  :scopes,       null: false, default: ''
-      t.timestamps
+      t.timestamps null: true
     end
 
     add_index :oauth_applications, :uid, unique: true

db/migrate/20150108073740_create_application_settings.rb

 # rubocop:disable all
 class CreateApplicationSettings < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :application_settings do |t|
       t.integer :default_projects_limit
@@ -8,7 +10,7 @@ class CreateApplicationSettings < ActiveRecord::Migration
       t.boolean :gravatar_enabled
       t.text :sign_in_text
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20150313012111_create_subscriptions_table.rb

 # rubocop:disable all
 class CreateSubscriptionsTable < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :subscriptions do |t|
       t.integer :user_id
       t.references :subscribable, polymorphic: true
       t.boolean :subscribed
-      
-      t.timestamps
+
+      t.timestamps null: true
     end
 
-    add_index :subscriptions, 
+    add_index :subscriptions,
               [:subscribable_id, :subscribable_type, :user_id],
               unique: true,
               name: 'subscriptions_user_id_and_ref_fields'

db/migrate/20150501095306_create_licenses.rb

 class CreateLicenses < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :licenses do |t|
       t.text :data, null: false
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20150507194350_create_historical_data.rb

 class CreateHistoricalData < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :historical_data do |t|
       t.date :date, null: false
       t.integer :active_user_count
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20150609113337_create_approves.rb

 class CreateApproves < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :approvals do |t|
       t.integer :merge_request_id, null: false
       t.integer :user_id, null: false
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20150707222220_add_approvers_table.rb

 class AddApproversTable < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :approvers do |t|
       t.integer :target_id, null: false
       t.string :target_type
       t.integer :user_id, null: false
 
-      t.timestamps
+      t.timestamps null: true
 
       t.index [:target_id, :target_type]
       t.index :user_id

db/migrate/20150806104937_create_abuse_reports.rb

 # rubocop:disable all
 class CreateAbuseReports < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :abuse_reports do |t|
       t.integer :reporter_id
       t.integer :user_id
       t.text :message
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20151103134857_create_lfs_objects.rb

 # rubocop:disable all
 class CreateLfsObjects < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :lfs_objects do |t|
       t.string :oid, null: false, unique: true
       t.integer :size, null: false
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20151103134958_create_lfs_objects_projects.rb

 # rubocop:disable all
 class CreateLfsObjectsProjects < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :lfs_objects_projects do |t|
       t.integer :lfs_object_id, null: false
       t.integer :project_id, null: false
 
-      t.timestamps
+      t.timestamps null: true
     end
 
     add_index :lfs_objects_projects, :project_id

db/migrate/20151105094515_create_releases.rb

 # rubocop:disable all
 class CreateReleases < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :releases do |t|
       t.string :tag
       t.text :description
       t.integer :project_id
 
-      t.timestamps
+      t.timestamps null: true
     end
 
     add_index :releases, :project_id

db/migrate/20160212123307_create_tasks.rb

 # rubocop:disable all
 class CreateTasks < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :tasks do |t|
       t.references :user, null: false, index: true
@@ -9,7 +11,7 @@ class CreateTasks < ActiveRecord::Migration
       t.integer :action, null: false
       t.string :state, null: false, index: true
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20160416180807_add_award_emoji.rb

 # rubocop:disable all
 class AddAwardEmoji < ActiveRecord::Migration
+  DOWNTIME = false
+
   def change
     create_table :award_emoji do |t|
       t.string :name
       t.references :user
       t.references :awardable, polymorphic: true
 
-      t.timestamps
+      t.timestamps null: true
     end
 
     add_index :award_emoji, :user_id

db/migrate/20160831214002_create_project_features.rb

@@ -10,7 +10,7 @@ class CreateProjectFeatures < ActiveRecord::Migration
       t.integer  :snippets_access_level
       t.integer  :builds_access_level
 
-      t.timestamps
+      t.timestamps null: true
     end
   end
 end

db/migrate/20160916101334_add_approver_groups.rb

@@ -14,7 +14,7 @@ class AddApproverGroups < ActiveRecord::Migration
       t.string :target_type, null: false
       t.integer :group_id, null: false
 
-      t.timestamps
+      t.timestamps null: true
 
       t.index [:target_id, :target_type]
       t.index :group_id