Disable group-level integration testing feature

Currently, the integration testing feature is coupled to projects and
broken for a lot of integrations
https://gitlab.com/gitlab-org/gitlab/-/issues/213123. We can now save
integrations that belongs to a group
https://gitlab.com/gitlab-org/gitlab/-/merge_requests/39959 but we
should skip the integration testing feature as we do for instance-level
integrations.

app/models/service.rb

@@ -351,10 +351,10 @@ class Service < ApplicationRecord
     { success: result.present?, result: result }
   end
 
-  # Disable test for instance-level services.
+  # Disable test for instance-level and group-level services.
   # https://gitlab.com/gitlab-org/gitlab/-/issues/213138
   def can_test?
-    !instance?
+    !instance? && !group_id
   end
 
   # Returns a hash of the properties that have been assigned a new value since last save,

spec/models/service_spec.rb

@@ -171,6 +171,16 @@ RSpec.describe Service do
           it { is_expected.to be_falsey }
         end
       end
+
+      context 'when group-level service' do
+        Service.available_services_types.each do |service_type|
+          let(:service) do
+            service_type.constantize.new(group_id: group.id)
+          end
+
+          it { is_expected.to be_falsey }
+        end
+      end
     end
 
     describe '#test' do