Merge branch '56110-cluster-kubernetes-api-500-error-on-post-request' into 'master'

Improves restriction of multiple Kubernetes clusters via API

Closes #56110

See merge request gitlab-org/gitlab-ce!24251

2 files changed, 3 insertions, 3 deletions

diff --git a/lib/api/helpers.rb b/lib/api/helpers.rb
index 74927b4db81..fa6c9777824 100644
--- a/lib/api/helpers.rb
+++ b/lib/api/helpers.rb
@@ -235,8 +235,8 @@ module API
       forbidden! unless current_user.admin?
     end
 
-    def authorize!(action, subject = :global)
-      forbidden! unless can?(current_user, action, subject)
+    def authorize!(action, subject = :global, reason = nil)
+      forbidden!(reason) unless can?(current_user, action, subject)
     end
 
     def authorize_push_project
diff --git a/lib/api/project_clusters.rb b/lib/api/project_clusters.rb
index 7aada260297..c96261a7b57 100644
--- a/lib/api/project_clusters.rb
+++ b/lib/api/project_clusters.rb
@@ -63,7 +63,7 @@ module API
         use :create_params_ee
       end
       post ':id/clusters/user' do
-        authorize! :create_cluster, user_project
+        authorize! :add_cluster, user_project, 'Instance does not support multiple Kubernetes clusters'
 
         user_cluster = ::Clusters::CreateService
           .new(current_user, create_cluster_user_params)