[Dovecot] How is the correct "auth" method selected in 1.0-stable?

[Ben Beuchler]

In the example config for 1.0-stable, I see several "auth <blah> {}"
blocks.  The only one uncommented is the "auth default{}" block.  How
does dovecot decide which one to use?  If I want it to use LDAP,
should I just modify the "userdb" and "passdb" entries in the "auth
default" block?  Or should I be using the "auth ldap" block and
somehow telling dovecot to use it?

Thanks!

-Ben