Analyzing CAMARA Error grouping

[PedroDiez]

Problem description
CAMARA Errors are grouped in to three categories: syntax, service, server exceptions.
CAMARA-API-Design-Guide.md#31

There are some doubts regarding the allocation of some Errors within this grouping rules.

Example: New 409 error code called WRONG_STATE discussion

Expected action
Re-group exceptions based on agreements reached

Additional context
Issue proposed for M2

[PedroDiez]

Initial input for discussion:

• Probably Errors 403 and 409 fit better in "service" exceptions group as they determine business logic/conditions.
• Rest of errors would be kept as currently agrupation

[Kevsy]

I think the whole classification can be simplified:

• Syntax exception:
  The client has made a request with invalid syntax, and re-sending the same request will always result in the same exception.
  The server should indicate to the client what modification is required for the request to be resubmitted.
  Examples: 400 Bad request, 405 Method Unacceptable, etc.
• Service exception:
  The client has made a request with valid syntax, but the server is currently unable to fulfil it.
  This can be due to a technical reason (e.g. server or backend failure) or a policy reason (e.g. business quota exceeded)
  The server should indicate to the client if/when the request can be resubmitted and whether any modification is required.
  Examples 422 Unprocessable Entity, 429 QUOTA EXCEEDED, 5xx range

Note: when we did the error taxonomy in the OMA RESTful Network API specification some years ago, we also had 'Policy exception' as a distinct category. But I think it's simpler to have the two categories, as it helps show 'Client needs to change something' or 'Client is fine, server is having problems, and here is what to do next'