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