How to Allow UniqueMember to add under PosiGroup (UniqueueMemberof Plugins)

[Fosiul alam]

Hi,
I have installed this test ldap and I am trying to add  UniqueMember
under a PosixGroup

but its saying, i am not allowed bellow is error:

"according to the schema attribute uniqueMember is not allowed"


I guess, I need to add UniqueueMemberof plugins,

But dont understande the Syntax.
Can any one please help me with the syntax.

Kind Regards