Bring the v2 avatar webtest to 1:1 parity with the v1 avatar tests so
the v1 routes and tests can be removed without losing coverage:
- link-share auth path: a request authenticated as a link-share user
(not a regular JWT) returns 200 + non-empty image bytes, porting
v1's TestLinkShareAvatar.
- bot user: the botmarble provider path returns 200 + SVG bytes, a
distinct rendering v1 never exercised; asserts the marble mask id so
it cannot silently fall through to the default placeholder.
- non-numeric size: rejected with 422 (Huma's int64 query validation)
rather than v1's 400 ErrInvalidModel, both being client errors that
refuse the malformed input.
Add GET /api/v2/avatar/{username}, the v2 reference for a binary response
modeled in the OpenAPI spec. Reuses the v1 avatar provider logic (provider
lookup, size clamp to config.ServiceMaxAvatarSize, runtime content-type) and
returns raw image bytes via Huma's []byte body + dynamic Content-Type header
idiom, advertised in the spec as application/octet-stream.
The endpoint is authenticated under the global security like every other v2
route (an anonymous request gets a 401); it is not public.
kolaente