Auth credentials not honored on Livekit Cloud

[RenegadeMaster]

When creating a Livekit Cloud inbound trunk as per https://docs.livekit.io/sip/quickstarts/configuring-sip-trunk/
It is possible to add a username and password.
This can also be added retroactively with the lk CLI tool as e.g.:

lk sip inbound update --id ST_ID_HERE --auth-user test --auth-pass test123

However whatever username and password is set will simply not work. We get the following response:

"[2025-04-14 14:04:43] WARNING[1202949]: res_pjsip_outbound_registration.c:1440 handle_registration_response: '405' fatal response received from 'sip:5mjicw2rw4y.sip.livekit.cloud:5060' on registration attempt to 'sip:[email protected]:5060', retrying in '30' seconds"

Without username and password everything works fine.

See also https://livekit-users.slack.com/archives/C07FRP66XGE/p1745176433935169