Some deployments already have users that authenticate without a domain.
Today, we refuse to even consider those, and reject them at parsing time.
However, it is a use-case worth supporting, at least with some
restrictions that make the complexity manageable.
This patch changes the auth package to support authenticating users
without an "@domain" part.
Those requests will always be directly passed on to the fallback
authenticator, if available.
The dovecot fallback authenticator can already handle this case just fine.
This patch adds a section on dovecot authentication troubleshooting,
with common suggestions that can help identify what is going on when
the chasquid-dovecot interaction isn't working as expected.
In authentication requests sent to dovecot, chasquid uses the full
addresses, "user@domain". However this wasn't mentioned in the
documentation, and could cause some confusion.
So this patch adds an explicit clarification about this in the dovecot
integration documentation.
This patch adds dovecot support to the chasquid daemon, using the
internal dovecot library added in previous patches.
Dovecot support is still considered EXPERIMENTAL and may be reverted, or
changed in backwards-incompatible ways.
The patch also adds the corresponding integration test, which brings up
a dovecot server with a custom configuration, and tests chasquid's
authentication against it. If dovecot is not installed, the test is
skipped.
