feat: add debug_getRawHeader method

[natanasow]

Description

Currently, we're missing the debug_getRawHeader method.

Solution

• Implement debug_getRawHeader method
• Check conformity tests
• Edit openrpc.json and rpc-api.md
• Add tests (if needed)

Missing fields in the Hedera concept:

fee_recipient

• Address that receives transaction priority fees and MEV for the block
• Set by the block proposer
• Separates who proposes the block from who gets paid

prev_randao

• On-chain randomness value from the Proof-of-Stake RANDAO
• Used for validator selection and committee assignments
• Represents accumulated randomness up to the previous step (not perfectly random)

withdrawal_root

• Merkle root committing to all validator withdrawals in the block
• Links consensus-layer withdrawals to execution-layer processing

RPC method:

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "debug_getRawHeader",
  "params": [
    "latest" // block number or block hash
  ]
}

Response:

{
  "jsonrpc": "2.0",
  "id": 1,
  "result": "0xf90211a0..." // RLP encoded header
}

Note:

• fee_recipient - use 0.0.801 based on https://hips.hedera.com/hip/hip-1259
• prevRandao - use block.difficulty - 0x0
• withdrawal_root - use computed hash of an empty Trie object - 0x56e81f171bcc55a6ff8345e692c0f86e5b48e01b996cadc001622fb5e363b421

Related issue(s)

Fixes #4891

Testing Guide

Changes from original design (optional)

N/A

Additional work needed (optional)

N/A

Checklist

• I've assigned an assignee to this PR and related issue(s) (if applicable)
• I've assigned a label to this PR and related issue(s) (if applicable)
• I've assigned a milestone to this PR and related issue(s) (if applicable)
• I've updated documentation (code comments, README, etc. if applicable)
• I've done sufficient testing (unit, integration, etc.)

[github-actions]

Test Results

0 tests  ±0   0 ✅ ±0   0s ⏱️ ±0s
0 suites ±0   0 💤 ±0 
0 files   ±0   0 ❌ ±0 

Results for commit 6903a5f. ± Comparison against base commit c0f85f4.

♻️ This comment has been updated with latest results.

[jasuwienas]

lgtm...

It’s unfortunate that we have to fetch all the transactions in a block just to return the header. However, as long as we’re responsible for calculating the root, I don’t think there’s any way around it.

Just few nits to consider (non-blockers I guess)

EDIT: but you'llhave to resolve the conflicts first.

The base branch was changed.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

@@            Coverage Diff             @@
##             main    #4926      +/-   ##
==========================================
- Coverage   95.86%   95.67%   -0.20%     
==========================================
  Files         143      143              
  Lines       23968    24024      +56     
  Branches     1900     1895       -5     
==========================================
+ Hits        22977    22985       +8     
- Misses        967     1015      +48     
  Partials       24       24              

Flag	Coverage Δ
config-service	98.63% <ø> (ø)
relay	92.37% <100.00%> (+0.19%)	⬆️
server	88.39% <ø> (ø)
ws-server	97.90% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
packages/relay/src/index.ts	100.00% <100.00%> (ø)
packages/relay/src/lib/debug.ts	97.87% <100.00%> (+0.09%)	⬆️
packages/relay/src/lib/factories/blockFactory.ts	98.55% <100.00%> (+12.83%)	⬆️

... and 11 files with indirect coverage changes

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