Return http status 204 on deletes

Closes #2871
- Refactor api http handlers.
- Update tests.
- Remove special handling of responses in ember adapter.

ghost/admin/app/adapters/base.js

@@ -41,20 +41,6 @@ export default RESTAdapter.extend(DataAdapterMixin, {
         return url;
     },
 
-    // Override deleteRecord to disregard the response body on 2xx responses.
-    // This is currently needed because the API is returning status 200 along
-    // with the JSON object for the deleted entity and Ember expects an empty
-    // response body for successful DELETEs.
-    // Non-2xx (failure) responses will still work correctly as Ember will turn
-    // them into rejected promises.
-    deleteRecord() {
-        let response = this._super(...arguments);
-
-        return response.then(() => {
-            return null;
-        });
-    },
-
     handleResponse(status) {
         if (status === 401) {
             if (this.get('session.isAuthenticated')) {

ghost/admin/app/mirage/config.js

@@ -125,6 +125,12 @@ export default function () {
         return response;
     });
 
+    this.del('/posts/:id/', function (db, request) {
+        db.posts.remove(request.params.id);
+
+        return new Mirage.Response(204, {}, {});
+    });
+
     /* Roles ---------------------------------------------------------------- */
 
     this.get('/roles/', function (db, request) {
@@ -267,7 +273,11 @@ export default function () {
         };
     });
 
-    this.del('/tags/:id/', 'tag');
+    this.del('/tags/:id/', function (db, request) {
+        db.tags.remove(request.params.id);
+
+        return new Mirage.Response(204, {}, {});
+    });
 
     /* Users ---------------------------------------------------------------- */
 
@@ -304,7 +314,11 @@ export default function () {
         };
     });
 
-    this.del('/users/:id/', 'user');
+    this.del('/users/:id/', function (db, request) {
+        db.users.remove(request.params.id);
+
+        return new Mirage.Response(204, {}, {});
+    });
 
     this.get('/users/:id', function (db, request) {
         return {