GraphQL - subscription

### Is your feature request related to a problem?

It is no more possible to subscribe to all events only to one specific transaction

### Describe the solution you'd like

Need a more advanced subscription method, based on one address as today, on the first address of the chain, type of transaction, all transactions etc…

### Additional context

_No response_

Start by reading the existing GraphQL subscription entry point and documenting how the current address-based subscription works. Clarify the supported event and transaction filters, then define done as subscriptions being able to target the requested transaction scopes and having coverage for those cases.

Written by the indexing model from the issue text.