[BUG] Small organizations have problems with auth when small number of users and data changed

[stdevPavelmc]

Describe the bug Scenario:

• A small organization, 50 users not concurrently, tops 10-15 users using the emails daily.
• You create a user and forget to set the Quota or another LDAP parameter.
• The user tried to login and failed (dovecot auth cache hit as user auth successfully)
• You changed the parameter but the user can get in yet...
• Dovecot auth cache has data as valid and even auth is valid so no cache update we still has the bad data in cache.

Investigation auth_cache_ttl = 1hour auth_cache_size = 1M (~200 bytes per user )

Thinking over this, we can lower the auth_cache_ttl to 10 minutes and rise the auth_cache_size, so we can cache more entries and it will timeout sooner... Ano other thoughts?

[stdevPavelmc]

Proposed fix is working, PR in the way

[stdevPavelmc]

Closed by #108