GRN2-xx: Switch the relation between users and roles to make queries cleaner and faster (#1299)

* First steps

* Fixes in account creation flow

* Fixed most testcases

* more test fixes

* Fixed more test cases

* Passing tests and rubocop

* Added rake task to remove rooms

db/migrate/20190314152108_rolify_create_roles.rb

@@ -19,7 +19,7 @@ class RolifyCreateRoles < ActiveRecord::Migration[5.0]
     add_index(:users_roles, [:user_id, :role_id])
 
     User.all.each do |user|
-      user.add_role(:user) if user.roles.blank?
+      user.set_role(:user) if user.roles.blank?
     end
   end
 end

db/migrate/20200413150518_add_role_id_to_users.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+class MigrationProduct < ActiveRecord::Base
+  self.table_name = :users
+end
+
+class SubMigrationProduct < ActiveRecord::Base
+  self.table_name = :roles
+end
+
+class AddRoleIdToUsers < ActiveRecord::Migration[5.2]
+  def change
+    reversible do |dir|
+      dir.up do
+        add_reference :users, :role, index: true
+
+        MigrationProduct.where(role_id: nil).each do |user|
+          highest_role = SubMigrationProduct.joins("INNER JOIN users_roles ON users_roles.role_id = roles.id")
+                                            .where("users_roles.user_id = '#{user.id}'").min_by(&:priority).id
+          user.update_attributes(role_id: highest_role) unless highest_role.nil?
+        end
+      end
+
+      dir.down do
+        remove_reference :users, :role, index: true
+      end
+    end
+  end
+end

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: 2020_01_30_144841) do
+ActiveRecord::Schema.define(version: 2020_04_13_150518) do
 
   create_table "features", force: :cascade do |t|
     t.integer "setting_id"
@@ -120,11 +120,13 @@ ActiveRecord::Schema.define(version: 2020_01_30_144841) do
     t.string "activation_digest"
     t.datetime "activated_at"
     t.boolean "deleted", default: false, null: false
+    t.integer "role_id"
     t.index ["created_at"], name: "index_users_on_created_at"
     t.index ["deleted"], name: "index_users_on_deleted"
     t.index ["email"], name: "index_users_on_email"
     t.index ["password_digest"], name: "index_users_on_password_digest", unique: true
     t.index ["provider"], name: "index_users_on_provider"
+    t.index ["role_id"], name: "index_users_on_role_id"
     t.index ["room_id"], name: "index_users_on_room_id"
   end