feat: add useRcBlockFormat parameter for RC block response formatting

[TarikGul]

Summary

Adds useRcBlockFormat query parameter to control response format when using useRcBlock=true.

• array (default): Returns existing array format
• object: Wraps response with rcBlock info and parachainDataPerBlock array

Example

GET /accounts/{accountId}/balance-info?at=1000000&useRcBlock=true&useRcBlockFormat=object

Returns:

{
  "rcBlock": {
    "hash": "0x...",
    "parentHash": "0x...",
    "number": "1000000"
  },
  "parachainDataPerBlock": [...]
}

[TarikGul]

closes: #1821

[andrew-ifrita]

Looks fine, so I will approve.

It may be a cleaner and cut down on all the duplication if we just have a responseFormatter middleware. It will also cut down on human error as endpoints are added and changed if someone forgets to add this formatting. It also give a single place to look for output formatting, which we could later document and would probably be nice to know as a developer coming in with little context.

Naming-wise, I would consider a better name, but I am not sure what to suggest. Something like format=rc might work and might be more intuitive and flexible but I am uncertain on the naming side.

[TarikGul]

responseFormatter middleware

I totally agree, i think this would be a good ethos to bring to polkadot-rest-api. I'll merge for now and create a follow up issue.