@Override
    public void deleteMember(String groupName, JID user)
    {
        getGroupProvider(groupName).deleteMember(groupName, user);
    }
Deletes an entity from a group (optional operation).

Implementations should use the bare JID representation of the JID passed as an argument to this method.

@param groupName the group name.
@param user the (bare) JID of the entity to delete.
@throws UnsupportedOperationException if the provider does not support the operation.
xmppserver/src/main/java/org/jivesoftware/openfire/group/GroupMultiProvider.java