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

app/controllers/sessions_controller.rb

@@ -218,7 +218,7 @@ class SessionsController < ApplicationController
 
     # Add pending role if approval method and is a new user
     if approval_registration && !@user_exists
-      user.add_role :pending
+      user.set_role :pending
 
       # Inform admins that a user signed up if emails are turned on
       send_approval_user_signup_email(user)
@@ -228,6 +228,8 @@ class SessionsController < ApplicationController
 
     send_invite_user_signup_email(user) if invite_registration && !@user_exists
 
+    user.set_role :user unless @user_exists
+
     login(user)
 
     if @auth['provider'] == "twitter"