Add extra checks for project-specific views

Some parts of integrations are only meant for projects.
They fail to render if a project is not available, so it's
best to hide them for now on group/instance level
integrations.

https://gitlab.com/gitlab-org/gitlab/-/issues/298854

app/models/service.rb

@@ -413,6 +413,10 @@ def can_test?
     !instance? && !group_id
   end
 
+  def project_level?
+    project_id.present?
+  end
+
   def parent
     project || group
   end

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

@@ -10,8 +10,8 @@
     %p.inline
       = s_("MattermostService|See list of available commands in Mattermost after setting up this service, by entering")
     %kbd.inline /<trigger> help
-    - unless enabled || @service.template?
+    - if !enabled && @service.project_level?
       = render 'projects/services/mattermost_slash_commands/detailed_help', subject: @service
 
-- if enabled && !@service.template?
+- if enabled && @service.project_level?
   = render 'projects/services/mattermost_slash_commands/installation_info', subject: @service

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

@@ -11,7 +11,7 @@
     %p.inline
       = s_("SlackService|See list of available commands in Slack after setting up this service, by entering")
     %kbd.inline /<command> help
-    - unless @service.template?
+    - if @service.project_level?
       %p= _("To set up this service:")
       %ul.list-unstyled.indent-list
         %li

changelogs/unreleased/298854-gitlab-returns-error-500-when-visiting-admin-area-settings-integra.yml

+---
+title: Hide project-specific views on group / instance level integrations
+merge_request: 57381
+author:
+type: fixed

ee/app/views/projects/services/gitlab_slack_application/_help.html.haml

@@ -6,5 +6,5 @@
     %p.inline
       = _("See the list of available commands in Slack after setting up this service by entering")
   %kbd.inline /gitlab help
-  - unless @service.template? || @service.instance?
+  - if @service.project_level?
     = render "projects/services/#{@service.to_param}/slack_integration_form"

spec/models/service_spec.rb

@@ -202,6 +202,16 @@
     end
   end
 
+  describe '#project_level?' do
+    it 'is true when service has a project' do
+      expect(build(:service, project: project)).to be_project_level
+    end
+
+    it 'is false when service has no project' do
+      expect(build(:service, project: nil)).not_to be_project_level
+    end
+  end
+
   describe '.find_or_initialize_non_project_specific_integration' do
     let!(:service1) { create(:jira_service, project_id: nil, group_id: group.id) }
     let!(:service2) { create(:jira_service) }