Which address should a multi-ORPort Tor put in its "transport" extra-info line?
https://gitlab.torproject.org/tpo/core/torspec/-/blob/main/dir-spec.txt#L907
When a bridge advertises its pluggable transports to BridgeDB, it adds its external IP address in its "transport" line in its extrainfo descriptor.
We should clearly spec out what a bridge should put in its "transport" line when it has multiple OR addresses.