Demo does not work

The demo Url: http://ang-exp-blog.briantford.com/

Failing to load/add blog posts.

Error got in the console:
`Failed to load resource: the server responded with
a status of 500 (Internal Server Error)
http://ang-exp-blog.briantford.com/api/posts`

Reproduce the failure at http://ang-exp-blog.briantford.com/ and inspect the /api/posts request shown in the console. Trace the backend route and its error output to identify why loading and adding posts return HTTP 500. Done means the demo can load and add blog posts successfully without that server error.

Written by the indexing model from the issue text.