API: Return 400 when creating a systemhook fails

changelogs/unreleased/api-return-400-if-post-systemhook-fails.yml

+---
+title: Return 400 when creating a system hook fails
+merge_request: 7350
+author: Robert Schilling

lib/api/system_hooks.rb

@@ -32,7 +32,7 @@ module API
         if hook.save
           present hook, with: Entities::Hook
         else
-          not_found!
+          render_validation_error!(hook)
         end
       end
 

spec/requests/api/system_hooks_spec.rb

@@ -52,6 +52,12 @@ describe API::API, api: true  do
       expect(response).to have_http_status(400)
     end
 
+    it "responds with 400 if url is invalid" do
+      post api("/hooks", admin), url: 'hp://mep.mep'
+
+      expect(response).to have_http_status(400)
+    end
+
     it "does not create new hook without url" do
       expect do
         post api("/hooks", admin)