On-device test against Sonos showed SetAVTransportURI returning UPnP
error 714 (IllegalMimeType). Logcat:
POST /api/cast/stream-token -> 200 (token minted)
SetAVTransportURI to http://minstrel.fabledsword.com/...
<-- 500 from Sonos: SoapFaultException SOAP fault 714
The server is behind a TLS-terminating reverse proxy, so r.TLS is
nil and the URL builder emitted http://. Sonos does a HEAD probe to
detect the audio MIME type; against an http:// URL that 301s to
https://, the probe finds no audio body and bails with 714.
The Task 2 code-quality reviewer flagged this exact scenario at the
time. Closing it now: honor X-Forwarded-Proto + X-Forwarded-Host
before falling back to r.TLS + r.Host. Public URL the speaker
fetches now matches the scheme/host the client used to reach the
endpoint.
bvandeusen
7d15f57e86