This is something that few people use, so it hasn’t really seen much documentation. It just went in during the original implementation in case someone wanted it. Wildcards are not supported, but there is a domain alias type[1] which I believe would be like:
[bob.com]
type=domain_alias
domain=joe.com
To alias “bob.com” to “joe.com” though having not touched it in probably 8 years that’s just going by memory.
[1] asterisk/pjsip.conf.sample at master · asterisk/asterisk · GitHub