Added feature flag around release link urls

Added feature flags in Release API entity class.
Removed mentions of mr and issues urls in API doc.

doc/api/releases/index.md

@@ -122,10 +122,6 @@ Example response:
             }
          ]
       },
-      "_links":{
-         "merge_requests_url": "https://gitlab.example.com/root/awesome_app/merge_requests?release_tag=v0.2&scope=all&state=opened",
-         "issues_url": "https://gitlab.example.com/root/awesome_app/issues?release_tag=v0.2&scope=all&state=opened"
-      }
    },
    {
       "tag_name":"v0.1",
@@ -182,10 +178,6 @@ Example response:
 
          ]
       },
-      "_links":{
-         "merge_requests_url": "https://gitlab.example.com/root/awesome_app/merge_requests?release_tag=v0.1&scope=all&state=opened",
-         "issues_url": "https://gitlab.example.com/root/awesome_app/issues?release_tag=v0.1&scope=all&state=opened"
-      }
    }
 ]
 ```
@@ -297,10 +289,6 @@ Example response:
 
       ]
    },
-   "_links":{
-      "merge_requests_url": "https://gitlab.example.com/root/awesome_app/merge_requests?release_tag=v0.1&scope=all&state=opened",
-      "issues_url": "https://gitlab.example.com/root/awesome_app/issues?release_tag=v0.1&scope=all&state=opened"
-   }
 }
 ```
 
@@ -426,10 +414,6 @@ Example response:
          }
       ]
    },
-   "_links":{
-      "merge_requests_url": "https://gitlab.example.com/root/awesome_app/merge_requests?release_tag=v0.3&scope=all&state=opened",
-      "issues_url": "https://gitlab.example.com/root/awesome_app/issues?release_tag=v0.3&scope=all&state=opened"
-   }
 }
 ```
 
@@ -531,10 +515,6 @@ Example response:
 
       ]
    },
-   "_links":{
-      "merge_requests_url": "https://gitlab.example.com/root/awesome_app/merge_requests?release_tag=v0.1&scope=all&state=opened",
-      "issues_url": "https://gitlab.example.com/root/awesome_app/issues?release_tag=v0.1&scope=all&state=opened"
-   }
 }
 ```
 
@@ -617,10 +597,6 @@ Example response:
 
       ]
    },
-   "_links":{
-      "merge_requests_url": "https://gitlab.example.com/root/awesome_app/merge_requests?release_tag=v0.1&scope=all&state=opened",
-      "issues_url": "https://gitlab.example.com/root/awesome_app/issues?release_tag=v0.1&scope=all&state=opened"
-   }
 }
 ```
 

lib/api/entities.rb

@@ -1315,8 +1315,8 @@ module API
         end
       end
       expose :_links do
-        expose :merge_requests_url
-        expose :issues_url
+        expose :merge_requests_url, if: -> (_) { release_mr_issue_urls_available? }
+        expose :issues_url, if: -> (_) { release_mr_issue_urls_available? }
       end
 
       private
@@ -1347,6 +1347,10 @@ module API
         { scope: 'all', state: 'opened', release_tag: object.tag }
       end
 
+      def release_mr_issue_urls_available?
+        ::Feature.enabled?(:release_mr_issue_urls, project)
+      end
+
       def project
         @project ||= object.project
       end