This plugin implements the default domain for an app, based on its name.
If an app's name contains a dot ('.'), it is interpreted as that app's default
domain. Otherwise, if a domain is defined for the server in
$PLUSHU_ROOT/APPS_DOMAIN, the app's default domain will be the name of the
app as a subdomain of APPS_DOMAIN (eg. if APPS_DOMAIN were example.com, and
an app were pushed named myapp, its defult domain would be
myapp.example.com).
This plugin also sets the default hostname from within the app's container to this default name.
See also plushu/plushu-domains, which allows for defining additional custom domains for an app.