Thanks! I will check AttributeS.
I have several services, essentially a zoo of kamailio/opensips, freeswitch and asterisk. Cgrates seemed like a good solution for me to store numbers. But not every service can provide me with an ID (from user), but I always have a caller_id_number from my pool, which is linked to its tenant.
The idea is that call services could create their own user in cgrates and the numbers associated with them with API (I think it will be a wrapper over cgrates), before user can be call.