Improve jupyter app db migrations

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

db/migrate/20180511131058_create_clusters_applications_jupyter.rb

@@ -9,15 +9,15 @@ class CreateClustersApplicationsJupyter < ActiveRecord::Migration
   def change
     create_table :clusters_applications_jupyter do |t|
       t.references :cluster, null: false, unique: true, foreign_key: { on_delete: :cascade }
-      t.references :oauth_application
+      t.references :oauth_application, foreign_key: { on_delete: :nullify }
 
       t.integer :status, null: false
       t.string :version, null: false
       t.string :hostname
 
-      t.text :status_reason
-
       t.timestamps_with_timezone null: false
+
+      t.text :status_reason
     end
   end
 end

db/schema.rb

@@ -2208,6 +2208,8 @@ ActiveRecord::Schema.define(version: 20180529093006) do
   add_foreign_key "clusters_applications_helm", "clusters", on_delete: :cascade
   add_foreign_key "clusters_applications_ingress", "clusters", name: "fk_753a7b41c1", on_delete: :cascade
   add_foreign_key "clusters_applications_prometheus", "clusters", name: "fk_557e773639", on_delete: :cascade
+  add_foreign_key "clusters_applications_jupyter", "clusters", on_delete: :cascade
+  add_foreign_key "clusters_applications_jupyter", "oauth_applications", on_delete: :nullify
   add_foreign_key "clusters_applications_runners", "ci_runners", column: "runner_id", name: "fk_02de2ded36", on_delete: :nullify
   add_foreign_key "clusters_applications_runners", "clusters", on_delete: :cascade
   add_foreign_key "container_repositories", "projects"