New version of Loopback uses an updated sequence.ts

[nymd]

The current sequence.ts is out of date. It still works but the structure of loopback's sequence has changed:

https://loopback.io/doc/en/lb4/REST-middleware-sequence.html

At the bottom there are instructions for migrating. It is unknown whether we need to do so at this point. The one breakage was that it dropped the CORS headers that it used to send by default. That has been fixed by adding them manually.