Unclear usage of the :filter argument

[MarvinKlar]

Hello everyone,

I am using the discourse ldap plugin: https://github.com/jonmbake/discourse-ldap-auth
This plugins provides :filter argument in it's configuration. It says: LDAP filter (for group based authentication)
I assume that you can define the users with this filter, which should be able to login to discourse (the forum).

But your documentation says: :filter is the LDAP filter used to search the user entry. It can be used in place of :uid for more flexibility. %{username} will be replaced by the user name processed by :name_proc.
I don't really understand the essence of this description.

Could you please explain this to me?
I am asking, because we REALLY need a way to limit the users which should be allowed to login to our disocurse forum.

If I misunderstood the filter attribute please let me know so I have the possibility to look for an alternative!

Thanks for your help!

[MarvinKlar]

Does anyone know how to use this filter?