Multitenant with pjsip and domainnames

I want to know how deal with multitenant and Asterisk. I know that there is option to add prefix/sufix to username but how confiure pjsip for multitenant service with domain names? I mean i want for example have 2+ extension with 100 as internal number but username should be like
100@client.first /secret
100@client.secon / secret
Is this possible ?