fix(ingestor-api): stricter collections endpoints

[alukach]

Reviewing #35, I realized that the Collections endpoints have a few issues around them.

1. the Collections loader is currently smothering any error that it encounters. It would be better to allow the error to raise to the controller where it can appropriately inform the client that the creation of the collection has failed.
2. When a record is created with a POST request, a 201 response should be returning the record that was just created:

   The HTTP 201 Created success status response code indicates that the request has succeeded and has led to the creation of a resource. The new resource, or a description and link to the new resource, is effectively created before the response is sent back and the newly created items are returned in the body of the message, located at either the URL of the request, or at the URL in the value of the Location header. (source)

3. If our API fails to create a resource due to some internal, that may not be an appropriate situation to throw a 400 response