Add more specific HTTP status codes to REST interface

[mjordan]

• Return a 404 Not found if the resource identified in "Resource-ID" is not found by the persist plugin; do this for GET/HEAD and PATCH but not for PUT
• Return a 409 Conflict is the resource identified by "Resource-Id" already exists and the method is PUT.
• Return a 400 Bad Request if the "Resource-Id" header is not present in a request

[whikloj]

I think the use of additional HTTP verbs seems cleaniest. You GET and if the response is 404 you can decide whether to request a check via PUT or POST.

[mjordan]

Yes, I agree. I'm going to delete my latest comment - I don't know what I was thinking... my comment was from the perspective of checking the fixity e.g. against Fedora, not Riprap's REST interface, which is intended to be used by clients such as Drupal to get information about the fixity check event... two different things.