Refactor IdGen to assign IDs on a per-call basis for streamed RPC responses, ensuring that all responses in a stream share the same ID as the originating request.

Description

In the existing setup, IdGen assigns unique IDs to each individual RPC request. This becomes problematic when streaming multiple responses, as each response should have an ID identical to that of the original request, according to the JSON RPC Spec.

Tasks

• 1. Refactor IdGen so that it applies ID on a per-call basis.