GRN2-xx: Made role priority unique scoped to provider (#942)

* Made role priority unique scoped to provider

* Fixed issues related to update_role after making role priority unique

db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 2019_11_28_212935) do
+ActiveRecord::Schema.define(version: 2020_01_30_144841) do
 
   create_table "features", force: :cascade do |t|
     t.integer "setting_id"
@@ -58,6 +58,7 @@ ActiveRecord::Schema.define(version: 2019_11_28_212935) do
     t.datetime "updated_at", null: false
     t.index ["name", "provider"], name: "index_roles_on_name_and_provider", unique: true
     t.index ["name"], name: "index_roles_on_name"
+    t.index ["priority", "provider"], name: "index_roles_on_priority_and_provider", unique: true
   end
 
   create_table "rooms", force: :cascade do |t|