Buypass fails due to lack of USER_AGENT header #144
Description
When using instant_acme with the Buypass directory URL (https://api.buypass.com/acme/directory), the server responds with the following error:
{"type":"urn:ietf:params:acme:error:malformed","title":"Bad Request","status":400,"detail":"User-Agent header is required","instance":"/acme/directory"}
Buypass requires a USER_AGENT header for all requests to their ACME server.