feat(scim): Add /ResourceTypes and /Schemas

[xlgmokha]

What kind of change does this PR introduce?

Feature. GET /scim/v2/ResourceTypes and GET /scim/v2/Schemas return an empty ListResponse.

Extracted from #2643

https://linear.app/supabase/issue/AUTH-1362/scim-discovery-endpoints

What is the current behavior?

ServiceProviderConfig returns a real document, but ResourceTypes and Schemas still return 501 in the RFC 7644 error form.

What is the new behavior?

Adds the query response form from RFC 7644, and both endpoints answer with an empty one. No resource types exist yet.

$ curl -s http://localhost:9999/scim/v2/Schemas | jq
{
  "schemas": [
    "urn:ietf:params:scim:api:messages:2.0:ListResponse"
  ],
  "totalResults": 0,
  "startIndex": 1,
  "itemsPerPage": 0,
  "Resources": []
}

Neither endpoint supports filtering. RFC 7644, Section 4:

Query parameters described in Section 3.4.2, such as filtering, sorting, and
pagination, SHALL be ignored. If a "filter" is provided, the service provider
SHOULD respond with HTTP status code 403 (Forbidden) to ensure that clients
cannot incorrectly assume that any matching conditions specified in a filter
are true.

$ curl -s 'http://localhost:9999/scim/v2/Schemas?filter=name%20eq%20%22User%22' | jq
{
  "schemas": [
    "urn:ietf:params:scim:api:messages:2.0:Error"
  ],
  "detail": "Filtering is not supported on this endpoint",
  "status": "403"
}

Additional context