new wrapper for medusa integration tests.
for now it is only applied to the modules directory, but it could be used in the api integration tests or any other integrations that requires a db and a server up and running.
It is not perfect, but I wanted to have something working and centralised before improving it, also avoiding too many conflicts with other prs
**What**
- Introduce link between Region and PaymentProvider
- Introduce API endpoint `GET /store/regions/:id/payment-providers` for retrieving providers by region
- Add tests for both