how to add new user in LDAP server from client

LDAP is a protocol designed to manage and provide directory services, so as to be able to centralize management of different IT resources such as user or computer accounts, application services, shared data etc. So the background idea is to make it possible for an admin to define the directory schema and then centrally populate the DB with data which then will be used by various clients.
You look like want LDAP to be dedicated storage of your jabber user information (so that these users are for ejabberd use only). So you want to define your unique directory schema and make ejabberd to understand how to modify data in it. It's theoretically possible if you are brave enough to rewrite ejabberd's LDAP support from scratch, but as it's not consistent with the very intent of the technology it's hard to expect the authors to make such modifications. There are other options to create dedicated storage for ejabberd user DB.
You could try to find some other way to add users to LDAP: I don't know if it's possible, but if I had such a problem, I would check if I can add some stub authentication DB that wouldn't contain any data, but instead write into it would invoke some external script that would make actual writing into LDAP. (So my configuration would contain two authentication sources: one for LDAP, and another fake).