Problem description: currently there is no ability to set multiple LDAP authentication providers or multiple "base dn".

Explanation: I run a local Kolab.org instance (which is an LDAP authentication provider) where I create a separate, new, local domain for each project I start. I want to be able to authenticate to Phabricator with each of these domains. However, currently I can set only one domain.

Solution implementation suggestion: my particular problem can be solved by converting the base dn variable into an array of strings which would be looped afterwards (similar to how the query filter is implemented currently, but with base dn array we'd have two nested authentication loops: parent for base dn and the child for query), however, I assume that there are users with different LDAP host's aswell, so maybe the possibility to define multiple LDAP authentication providers is a more suitable one.