Update placeholder copy for integrations

- Update copy for slash commands integrations.
- Move fallback to placeholder from model to HAML
view in case other places use the method.

app/models/project_services/alerts_service.rb

@@ -15,9 +15,7 @@ class AlertsService < Service
   before_validation :ensure_token, if: :activated?
 
   def url
-    if instance? || template?
-      return '<namespace / project>'
-    end
+    return if instance? || template?
 
     url_helpers.project_alerts_notify_url(project, format: :json)
   end

app/views/projects/services/alerts/_help.html.haml

 .js-alerts-service-settings{ data: { activated: @service.activated?.to_s,
   form_path: scoped_integration_path(@service),
-  authorization_key: @service.token, url: @service.url, learn_more_url: 'https://docs.gitlab.com/ee/user/project/integrations/generic_alerts.html' } }
+  authorization_key: @service.token, url: @service.url || _('<namespace / project>'), learn_more_url: 'https://docs.gitlab.com/ee/user/project/integrations/generic_alerts.html' } }

app/views/projects/services/mattermost_slash_commands/_detailed_help.html.haml

-- pretty_name = @project&.full_name || _('<project name / alias>')
+- pretty_name = @project&.full_name || _('<project name>')
 - run_actions_text = s_("ProjectService|Perform common operations on GitLab project: %{project_name}") % { project_name: pretty_name }
 
 %p= s_("ProjectService|To set up this service:")

app/views/projects/services/slack_slash_commands/_help.html.haml

-- pretty_name = @project&.full_name || _('<project name / alias>')
+- pretty_name = @project&.full_name || _('<project name>')
 - run_actions_text = s_("ProjectService|Perform common operations on GitLab project: %{project_name}") % { project_name: pretty_name }
 
 .info-well

locale/gitlab.pot

@@ -778,13 +778,16 @@ msgstr ""
 msgid "<code>\"johnsmith@example.com\": \"johnsmith@example.com\"</code> will add \"By <a href=\"#\">johnsmith@example.com</a>\" to all issues and comments originally created by johnsmith@example.com. By default, the email address or username is masked to ensure the user's privacy. Use this option if you want to show the full email address."
 msgstr ""
 
+msgid "<namespace / project>"
+msgstr ""
+
 msgid "<no name set>"
 msgstr ""
 
 msgid "<no scopes selected>"
 msgstr ""
 
-msgid "<project name / alias>"
+msgid "<project name>"
 msgstr ""
 
 msgid "<strong>%{group_name}</strong> group members"