Make endpoints return more helpful json decode failures

[jisantuc]

Overview

This PR makes endpoints return more helpful messages when JSON decoding fails. It overrides the method to create
messages from decode failures with special handling for circe decoding failures.

Checklist

• New tests have been added or existing tests have been modified

Notes

Unfortunately this only returns the first error. I believe that this is because tapir just uses the decode function instead of the decodeAccumulating function for getting the circe decode result. We could also provide a closer derivation that would override this behavior.

Here are some example responses:

 $ echo '{}' | http :9090/collections/berlin/items
HTTP/1.1 400 Bad Request
Content-Length: 56
Content-Type: text/plain; charset=UTF-8
Date: Fri, 30 Oct 2020 21:26:22 GMT

I expected to find a value at .id, but there was nothing


 $ echo '{"id": 3}' | http :9090/collections/berlin/items
HTTP/1.1 400 Bad Request
Content-Length: 70
Content-Type: text/plain; charset=UTF-8
Date: Fri, 30 Oct 2020 21:26:33 GMT

I found something unexpected at .id. I expected a value of type String

Testing Instructions

• start your server with transactions support -- ./scripts/server --with-transactions
• send an obviously bogus request to the collections post endpoint: echo '{}' | http :9090/collections
• correct the error it tells you about and send another post -- echo '{ YOUR CORRECTED JSON HERE }' | http :9090/collection
• you should get different errors every time you do what the server asks you for until you end up with a valid collection

Closes #427

[kbgg]

Thanks again for this, works perfectly in my testing