Added "mediaAPI" labs flag

refs https://github.com/TryGhost/Toolbox/issues/95

- A flag go control the Media API alpha feature

core/server/web/api/canary/admin/routes.js

@@ -238,6 +238,7 @@ module.exports = function apiRoutes() {
 
     // ## media
     router.post('/media/upload',
+        labs.enabledMiddleware('mediaAPI'),
         mw.authAdminApi,
         apiMw.upload.media('file', 'thumbnail'),
         apiMw.upload.mediaValidation({type: 'media'}),

core/shared/labs.js

@@ -29,6 +29,7 @@ const ALPHA_FEATURES = [
     'oauthLogin',
     'membersActivity',
     'cardSettingsPanel',
+    'mediaAPI',
     'membersAutoLogin'
 ];