Return merge-request state in API

- expose `has_conflicts` and `mergeable_discussions_state` in API
- add unit tests for the change

changelogs/unreleased/30161-expose-merge-request-status-in-api.yml

+---
+title: Expose mergeable state of a merge request
+merge_request: 18888
+author: briankabiro
+type: added

doc/api/merge_requests.md

@@ -304,7 +304,9 @@ Parameters:
     "task_completion_status":{
       "count":0,
       "completed_count":0
-    }
+    },
+    "has_conflicts": false,
+    "blocking_discussions_resolved": true
   }
 ]
 ```
@@ -453,7 +455,9 @@ Parameters:
     "task_completion_status":{
       "count":0,
       "completed_count":0
-    }
+    },
+    "has_conflicts": false,
+    "blocking_discussions_resolved": true
   }
 ]
 ```
@@ -606,7 +610,9 @@ Parameters:
   "task_completion_status":{
     "count":0,
     "completed_count":0
-  }
+  },
+  "has_conflicts": false,
+  "blocking_discussions_resolved": true
 }
 ```
 

lib/api/entities.rb

@@ -777,6 +777,10 @@ module API
       expose :squash
 
       expose :task_completion_status
+
+      expose :cannot_be_merged?, as: :has_conflicts
+
+      expose :mergeable_discussions_state?, as: :blocking_discussions_resolved
     end
 
     class MergeRequest < MergeRequestBasic

spec/requests/api/merge_requests_spec.rb

@@ -775,6 +775,8 @@ describe API::MergeRequests do
       expect(json_response['merge_error']).to eq(merge_request.merge_error)
       expect(json_response['user']['can_merge']).to be_truthy
       expect(json_response).not_to include('rebase_in_progress')
+      expect(json_response['has_conflicts']).to be_falsy
+      expect(json_response['blocking_discussions_resolved']).to be_truthy
     end
 
     it 'exposes description and title html when render_html is true' do