Add migration and feature in licence

Add migration that adds new settings to application settings

db/migrate/20200114140305_add_fields_to_application_settings_for_merge_requests_approvals.rb

+# frozen_string_literal: true
+
+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class AddFieldsToApplicationSettingsForMergeRequestsApprovals < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    add_column_with_default(:application_settings, :disable_overriding_approvers_per_merge_request,
+                            :boolean,
+                            default: false,
+                            allow_null: false)
+    add_column_with_default(:application_settings, :prevent_merge_requests_author_approval,
+                            :boolean,
+                            default: false,
+                            allow_null: false)
+    add_column_with_default(:application_settings, :prevent_merge_requests_committers_approval,
+                            :boolean,
+                            default: false,
+                            allow_null: false)
+  end
+
+  def down
+    remove_column(:application_settings, :disable_overriding_approvers_per_merge_request)
+    remove_column(:application_settings, :prevent_merge_requests_author_approval)
+    remove_column(:application_settings, :prevent_merge_requests_committers_approval)
+  end
+end

db/schema.rb

@@ -346,6 +346,9 @@ ActiveRecord::Schema.define(version: 2020_02_12_052620) do
     t.integer "elasticsearch_indexed_field_length_limit", default: 0, null: false
     t.integer "elasticsearch_max_bulk_size_mb", limit: 2, default: 10, null: false
     t.integer "elasticsearch_max_bulk_concurrency", limit: 2, default: 10, null: false
+    t.boolean "disable_overriding_approvers_per_merge_request", default: false, null: false
+    t.boolean "prevent_merge_requests_author_approval", default: false, null: false
+    t.boolean "prevent_merge_requests_committers_approval", default: false, null: false
     t.index ["custom_project_templates_group_id"], name: "index_application_settings_on_custom_project_templates_group_id"
     t.index ["file_template_project_id"], name: "index_application_settings_on_file_template_project_id"
     t.index ["instance_administration_project_id"], name: "index_applicationsettings_on_instance_administration_project_id"

ee/app/helpers/ee/application_settings_helper.rb

@@ -93,6 +93,9 @@ module EE
         default_project_deletion_protection
         deletion_adjourned_period
         updating_name_disabled_for_users
+        disable_overriding_approvers_per_merge_request
+        prevent_merge_requests_author_approval
+        prevent_merge_requests_committers_approval
       ]
     end
   end

ee/app/models/license.rb

@@ -80,6 +80,7 @@ class License < ApplicationRecord
     ldap_group_sync_filter
     merge_pipelines
     merge_request_performance_metrics
+    merge_request_approvers_rules
     merge_trains
     metrics_reports
     multiple_approval_rules