ReleaseEngineering/How Tos/Heroku:Add a custom domain
From MozillaWiki
Setup Heroku app with mozilla-releng.net subdomain and ssl endpoint
Heroku apps setup under Release Engineering can utilize the domain name '.mozilla-releng.net' and the associated Heroku ssl endpoint. Simply create a cname name pointed at oita-54541.herokussl.com and then add the new cname to the app as a custom domain.
Cnames can be setup under inventory.
$ heroku domains:add newherokuapp.mozilla-releng.net Adding newherokuapp.mozilla-releng.net to newherokuapp... done