Removes a role.

Every member stops being one, which can leave an account in no role at all, signed in and allowed nothing. That is a real state, not an error, and the listing shows how many accounts it would affect.

Errors

401 when nothing was signed in, 403 when the caller may not write roles or used a bearer token, 404 when no role has that identifier, 409 when it is a seeded role or the last one able to administer the instance.