Fix default emaildomain when creating RAT users

Remove hard coded example.com emaildomain for users that are added by
creating resource access tokens and set it to the instance hostname.
see Gitlab.config.gitlab['host']
Added spec test to ensure the RAT user email address domain is set as
wanted.

Changelog: fixed

app/services/resource_access_tokens/create_service.rb

@@ -75,7 +75,8 @@ module ResourceAccessTokens
     end
 
     def generate_email
-      email_pattern = "#{resource_type}#{resource.id}_bot%s@example.com"
+      # Default emaildomain need to be reworked. See gitlab-org/gitlab#260305
+      email_pattern = "#{resource_type}#{resource.id}_bot%s@noreply.#{Gitlab.config.gitlab.host}"
 
       uniquify.string(-> (n) { Kernel.sprintf(email_pattern, n) }) do |s|
         User.find_by_email(s)

doc/user/project/settings/project_access_tokens.md

@@ -170,11 +170,11 @@ selected role and [scope](#scopes-for-a-project-access-token) of the project acc
 
 - The name is set to the name of the token.
 - The username is set to `project_{project_id}_bot` for the first access token. For example, `project_123_bot`.
-- The email is set to `project{project_id}_bot@example.com`. For example, `project123_bot@example.com`.
+- The email is set to `project{project_id}_bot@noreply.{Gitlab.config.gitlab.host}`. For example, `project123_bot@noreply.example.com`.
 - For additional access tokens in the same project, the username is set to `project_{project_id}_bot{bot_count}`. For
   example, `project_123_bot1`.
-- For additional access tokens in the same project, the email is set to `project{project_id}_bot{bot_count}@example.com`.
-  For example, `project123_bot1@example.com`.
+- For additional access tokens in the same project, the email is set to `project{project_id}_bot{bot_count}@noreply.{Gitlab.config.gitlab.host}`.
+  For example, `project123_bot1@noreply.example.com`.
 
 API calls made with a project access token are associated with the corresponding bot user.
 

spec/services/resource_access_tokens/create_service_spec.rb

@@ -10,6 +10,10 @@ RSpec.describe ResourceAccessTokens::CreateService do
   let_it_be(:group) { create(:group, :private) }
   let_it_be(:params) { {} }
 
+  before do
+    stub_config_setting(host: 'example.com')
+  end
+
   describe '#execute' do
     shared_examples 'token creation fails' do
       let(:resource) { create(:project)}
@@ -88,6 +92,15 @@ RSpec.describe ResourceAccessTokens::CreateService do
         end
       end
 
+      context 'bot email' do
+        it 'check email domain' do
+          response = subject
+          access_token = response.payload[:access_token]
+
+          expect(access_token.user.email).to end_with("@noreply.#{Gitlab.config.gitlab.host}")
+        end
+      end
+
       context 'access level' do
         context 'when user does not specify an access level' do
           it 'adds the bot user as a maintainer in the resource' do