Database connections managment.

[Andrei-Dolgolev]

Moonstreamdb module

https://github.com/moonstream-to/api/blob/main/moonstreamdb/moonstreamdb/db.py

Currently we maintaine 2 connections to database with permissions Read/Write.

TODO:

We need create connection pool which can store RDS's connections and return them by customer_id.

Create Resolver.

        backend          |                               db module
`user_token` - > `user_id` -> `customer_id` -> RDS connection from sqlalchemy `customers_connections`