All API endpoints support integer project IDs, but a number of others
also support the URL-encoded form (e.g. `group%2Fproject`). For the sake
of consistency, Workhorse should match on both integer and encoded
formats. Endpoints that do not support the encoded form will return 400
whether they are accelerated by Workhorse or not.

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/324814