[scim] Uniqueness Violation Response Code

[Shelley <[e-mail]>]

RFC 7643 Section 7 [1] indicates the following:

uniqueness  A single keyword value that specifies how the service
>    provider enforces uniqueness of attribute values.
> *  A server MAY   reject an invalid value based on uniqueness by returning
> HTTP*
> *   response code 400 (Bad Request).*
>

This contradicts the requirements in RFC 7644 Section 3.3 [2] which
indicates that service providers "*MUST return HTTP status code 409
(Conflict)*" when the creation of a requested resource would conflict with
an existing resource, i.e. by violating an attribute's uniqueness.
Therefore, servers *MAY NOT* reject invalid values based on uniqueness with
a 400, as RFC 7643 Section 7 currently indicates.

I assume 409 is the preferred response here, and so I was initially going
to report an errata that proposed 409 instead of 400 in RFC 7643 Section 7;
however, to avoid dependencies on specific HTTP response codes from RFC
7644, I would propose the section could be updated as follows instead, such
that the HTTP response code is omitted entirely:

uniqueness  A single keyword value that specifies how the service
>    provider enforces uniqueness of attribute values.  A server MAY
>    reject an invalid value based on uniqueness.


Any feedback is welcome. I'm happy to report the proposed errata if there
is consensus; otherwise, I at least wanted to bring awareness to the
contradiction between specs here.

[1] https://tools.ietf.org/html/rfc7643#section-7
[2] https://tools.ietf.org/html/rfc7644#section-3.3