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 98.24561% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 82.0%. Comparing base (4dc923d) to head (4d91238).

Files with missing lines	Patch %	Lines
src/xrpld/rpc/handlers/account/AccountTx.cpp	96.8%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff            @@
##           develop   #6126     +/-   ##
=========================================
- Coverage     82.0%   82.0%   -0.0%     
=========================================
  Files         1010    1010             
  Lines        76304   76359     +55     
  Branches      7486    7479      -7     
=========================================
+ Hits         62535   62579     +44     
- Misses       13769   13780     +11     

Files with missing lines	Coverage Δ
include/xrpl/rdb/RelationalDatabase.h	100.0% <ø> (ø)
src/xrpld/app/misc/NetworkOPs.cpp	69.7% <100.0%> (ø)
src/xrpld/app/rdb/backend/detail/Node.cpp	60.5% <100.0%> (+1.8%)	⬆️
src/xrpld/rpc/handlers/account/AccountTx.cpp	87.9% <96.8%> (+1.3%)	⬆️

... 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?

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[Copilot]

Pull request overview

Adds a new delegate request parameter to the account_tx RPC to filter results based on delegated transaction signing (delegator vs delegatee scenarios).

Changes:

• Introduces DelegateFilter/DelegateType and parses the new delegate JSON node in account_tx.
• Propagates the filter into relational DB paging options and applies filtering while iterating transaction rows.
• Adds RPC unit tests validating correct filtering and malformed-parameter handling.

Reviewed changes

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

Show a summary per file

File	Description
src/xrpld/rpc/handlers/account/AccountTx.cpp	Parses the new delegate param and forwards it into DB paging options.
src/xrpld/app/rdb/backend/detail/Node.cpp	Applies delegate-based filtering during accountTxPage iteration by comparing tx owner vs signer.
src/xrpld/app/misc/NetworkOPs.cpp	Updates AccountTxPageOptions aggregate init to include the new delegate field.
src/test/rpc/AccountTx_test.cpp	Adds delegation filtering tests and malformed-input coverage.
src/test/rpc/AccountObjects_test.cpp	Minor test adjustment (const + designated initializer) unrelated to account_tx filtering.
include/xrpl/rdb/RelationalDatabase.h	Adds delegate filter types and threads delegate through relevant option/result structs.
include/xrpl/protocol/jss.h	Adds new JSON keys used by the feature (delegate_filter, counterparty, etc.).
.github/scripts/levelization/results/ordering.txt	Updates module dependency ordering for the new xrpl.rdb > xrpl.json relationship.

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[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.

[kuznetsss]

LGTM, one minor comment