add access restriction

app/controllers/users/omniauth_callbacks_controller.rb

 class Users::OmniauthCallbacksController < Devise::OmniauthCallbacksController
   def google_oauth2
+
+    email = request.env['omniauth.auth'].info['email']
+
+    # reject if email is not zigexn nor ventura
+    if email !~ /@zigexn\.co\.jp$/ && email !~ /@zigexn\.vn$/
+      redirect_to root_path, flash: { alert: 'Your email address is not permitted.' }
+      return
+    end
+
     # You need to implement the method below in your model (e.g. app/models/user.rb)
     @user = User.find_for_google_oauth2(request.env['omniauth.auth'], current_user)