I just opened a PR that adds deprecation notices to the response bodies
of requests to `/federation_resolvers/{{ID}}` and adds a DELETE method
handler to `/federation_resolvers`. That was the only method that
`/federation_resolvers/{{ID}}` handled, so with the handler addition to
`/federation_resolvers`, the former serves no purpose that the latter
cannot do equally well.So is it cool if we deprecate it?
