Answers ACME HTTP-01 challenges (RFC 8555, section 8.3). A request to /.well-known/acme-challenge/<token> for a host with a pending challenge gets the key authorization as application/octet-stream. Any other token gets 404. If the ACME account key cannot be processed, the response is a 500 internal problem detail. See the documentation of the acme element for the certificate setup.
