API: Add last_activity_at date to project entity

doc/api/projects.md

@@ -30,7 +30,8 @@ GET /projects
     "merge_requests_enabled": false,
     "wall_enabled": true,
     "wiki_enabled": true,
-    "created_at": "2012-05-23T08:05:02Z"
+    "created_at": "2012-05-23T08:05:02Z",
+    "last_activity_at": "2012-05-23T08:05:02Z"
   },
   {
     "id": 5,
@@ -52,7 +53,8 @@ GET /projects
     "merge_requests_enabled": true,
     "wall_enabled": true,
     "wiki_enabled": true,
-    "created_at": "2012-05-30T12:49:20Z"
+    "created_at": "2012-05-30T12:49:20Z",
+    "last_activity_at": "2012-05-23T08:05:02Z"
   }
 ]
 ```
@@ -92,7 +94,8 @@ Parameters:
   "merge_requests_enabled": true,
   "wall_enabled": true,
   "wiki_enabled": true,
-  "created_at": "2012-05-30T12:49:20Z"
+  "created_at": "2012-05-30T12:49:20Z",
+  "last_activity_at": "2012-05-23T08:05:02Z"
 }
 ```
 

lib/api/entities.rb

@@ -30,7 +30,7 @@ module API
       expose :owner, using: Entities::UserBasic
       expose :name, :name_with_namespace
       expose :path, :path_with_namespace
-      expose :issues_enabled, :merge_requests_enabled, :wall_enabled, :wiki_enabled, :created_at
+      expose :issues_enabled, :merge_requests_enabled, :wall_enabled, :wiki_enabled, :created_at, :last_activity_at
       expose :namespace
     end