Excludes project-only services from the admin service templates area

Introduces project_only method to the Service class that defaults to
false. When overridden in a subclass that service will not appear in
the list of service templates that can be set instance-wide.

Fixes a bug where the Generic Alerts Integration appeared at the top
of the list and produced an exception when clicked.

app/controllers/admin/services_controller.rb

@@ -7,7 +7,7 @@ class Admin::ServicesController < Admin::ApplicationController
   before_action :service, only: [:edit, :update]
 
   def index
-    @services = services_templates
+    @services = services_templates.reject(&:project_only?)
   end
 
   def edit

app/models/service.rb

@@ -330,6 +330,11 @@ class Service < ApplicationRecord
     false
   end
 
+  # Override for services supported at project level only
+  def project_only?
+    false
+  end
+
   private
 
   def cache_project_has_external_issue_tracker

ee/app/models/project_services/alerts_service.rb

@@ -58,6 +58,10 @@ class AlertsService < Service
     super || build_data
   end
 
+  def project_only?
+    true
+  end
+
   private
 
   def prevent_token_assignment

ee/spec/models/project_services/alerts_service_spec.rb

@@ -106,4 +106,8 @@ describe AlertsService do
       it_behaves_like 'valid token'
     end
   end
+
+  describe '#project_only?' do
+    it { expect(service).to be_project_only }
+  end
 end

spec/controllers/admin/services_controller_spec.rb

@@ -9,6 +9,15 @@ describe Admin::ServicesController do
     sign_in(admin)
   end
 
+  describe 'GET #index' do
+    it 'does not show project_only services' do
+      get :index
+
+      expect(assigns(:services)).not_to include(be_project_only),
+        "expected to exclude project_only services"
+    end
+  end
+
   describe 'GET #edit' do
     let!(:project) { create(:project) }
 

spec/models/service_spec.rb

@@ -399,6 +399,12 @@ describe Service do
     end
   end
 
+  describe '#project_only?' do
+    let(:service) { build_stubbed(:service, template: true) }
+
+    it { expect(service).not_to be_project_only }
+  end
+
   describe '#api_field_names' do
     let(:fake_service) do
       Class.new(Service) do