feat: Add delegate filter param for account_tx RPC

[PeterChen13579]

High Level Overview of Change

This PR adds the ability to filter account_tx results based on transaction delegation. This is useful for scenarios where one account (the delegatee) signs and submits a transaction on behalf of another account (the delegator).

Context of Change

New Request Parameter:

"delegate": {
"delegate_filter": "actor" or "authorizer",
"counter_party": "account_address"
}

Example: If User A submits a transaction to C on behalf of B:
User B (The account holder) can query with delegate_filter: "actor" to find transactions signed by others (like User A where A acted on behalf of B).
User A (The signer) can query with delegate_filter: "authorizer" to find transactions they signed for others (like User B, since B authorized A to act on their behalf).
The counter_party field can be used in either case to filter by a specific valid address

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactor (non-breaking change that only restructures code)
• Performance (increase or change in throughput and/or latency)
• Tests (you added tests for code that already exists, or your new feature included in this PR)
• Documentation update
• Chore (no impact to binary, e.g. .gitignore, formatting, dropping support for older tooling)
• Release

API Impact

• Public API: New feature (new methods and/or new fields)
• Public API: Breaking change (in general, breaking changes should only impact the next api_version)
• libxrpl change (any change that may affect libxrpl or dependents of libxrpl)
• Peer protocol change (must be backward compatible or bump the peer protocol version)

[codecov]

Codecov Report

❌ Patch coverage is 95.34884% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.6%. Comparing base (2b4d067) to head (f6c087c).

Files with missing lines	Patch %	Lines
src/xrpld/app/rdb/backend/detail/Node.cpp	93.0%	3 Missing ⚠️
src/xrpld/rpc/handlers/account/AccountTx.cpp	97.6%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           develop   #6126   +/-   ##
=======================================
  Coverage     82.6%   82.6%           
=======================================
  Files         1036    1036           
  Lines        79870   79953   +83     
  Branches      8949    8948    -1     
=======================================
+ Hits         65956   66039   +83     
  Misses       13905   13905           
  Partials         9       9           

Files with missing lines	Coverage Δ
include/xrpl/rdb/RelationalDatabase.h	100.0% <ø> (ø)
src/xrpld/app/misc/NetworkOPs.cpp	69.9% <100.0%> (ø)
src/xrpld/rpc/handlers/account/AccountTx.cpp	88.5% <97.6%> (+1.8%)	⬆️
src/xrpld/app/rdb/backend/detail/Node.cpp	61.3% <93.0%> (+2.4%)	⬆️

... and 4 files with indirect coverage changes

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[kuznetsss]

A few suggestions to the new API:

• don't duplicate delegate in filter:

"delegate": {
  "filter": "delegatee" or "delegator",
  "counter_party": "account_address"
}

• maybe use role instead of filter?

• I remember we had some other naming ideas for delegator and delegatee, did you decide that these one are the best?

[github-actions]

This PR has conflicts, please resolve them in order for the PR to be reviewed.

[github-actions]

All conflicts have been resolved. Assigned reviewers can now start or resume their review.

[github-actions]

This PR has conflicts, please resolve them in order for the PR to be reviewed.

[github-actions]

All conflicts have been resolved. Assigned reviewers can now start or resume their review.

[PeterChen13579]

/ai-review

[xrplf-ai-reviewer]

Good to go

Review by Claude Sonnet 4.6 · Prompt: V15

[godexsoft]

Few nits to fix/answer 👍

[godexsoft]

Looks good 👍

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated 5 comments.

[github-actions]

This PR has conflicts, please resolve them in order for the PR to be reviewed.

[github-actions]

All conflicts have been resolved. Assigned reviewers can now start or resume their review.

[bthomee]

Approving the latest commit containing newly added tests.