Help with auto proxy mod and custom container name

Noob alert. There might be a better/different way to accomplish what I want, but is it possible to use the auto proxy mod with a custom container name? For example, I’d like to make dokuwiki available at wiki.mydomain.com. If I change the dokuwiki container name to wiki and add a cname record for the wiki subdomain, then I just get a 400 bad request error because swag can’t resolve the wiki subdomain.

Related, for my own technical understanding, how does auto proxy know how to proxy a container name? Is it using the sample conf files in proxy-confs?