API Middleware/ gRPC gateway handling custom http response codes

[james-prysm]

🚀 Feature Request

Description

With more Rest based API integrations added to Prysm we need more flexibility with our API middleware/gRPC gateway setup. Currently, our API Middleware/ gRPC gateway setup doesn't allow us to return custom codes for successes (so only 200 ok)

these are the current mappings
Ideally, we would like a way to override this for more custom codes such as 202 on our API returns.

some examples where this is used.

1. keymanager api set fee recipient
2. blinded_block

Describe the solution you'd like

we should provide a way to customize a new gRPC option for custom returns
https://grpc-ecosystem.github.io/grpc-gateway/docs/mapping/customizing_your_gateway/#controlling-http-response-status-codes

[prestonvanloon]

Please also see https://github.com/grpc/grpc/blob/master/doc/statuscodes.md

[rkapka]

Closed with #10850