I am developing Freeswitch/FusipnPBX toact as a sip trunk service for customers. I see ways to configure gateways for my own upstream trunks, but I cannot seem to find any documentation regarding setting up a sip trunk that my customers would have to auth into to secure their service aside from no-auth no-reg and IP authentication with ACLs. Can this be done? I am specifically setting up an asterisk for a client PBX.