Guide to configure FusionPBX with ASTPP

I was wondering if anyone has produced a guide to configure FusionPBX with ASTPP? My providers SIP trunks should be configured within ASTPP as I understand it with all the other configuration set up at the FusionPBX end. External calls would be sent from FusionPBX and would terminate after the call has been routed through ASTPP. Any guide or info would be great to help me understand.
In ASTPP You keep your clients with billing ( call charges and monthly fees for DID's ). SIP device from ASTPP You need to setup as a gateway in Your FusionPBX domain. Then just create a inbound and outbound rules.
I assume you mean routing all calls via ASTPP. How would I get billing for outgoing calls per domain (tennet) in ASTPP? Unless 1) they only use callerid of their DID or 2) I setup separate gateways for each tenant. Also, for incoming I will need to setup all did's in both, Fusionpbx & ASTPP ?

I'm new in FusionPBX/Freeswitch and would like to integrate ASTPP for billing.
Does anyone had configured ASTPP as a gateway which could be the Trunk for FusionPBX?

ASTPP - Holds the VOIP Carriers and acts as a gateway Trunk (SIP/IP Auth/AIX2) and forward to the carrier to be log and billed.
FusionPBX - Act as a normal PBX (inbound and outbound would be routed over the SIP/IP/AIX2 if any for local trunking)

The design is attached below.

Kindly give me inputs and idea if this is doable.


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