feat: add versioned list endpoints (20260427) for transfers and cross-account transfers

[gerfboy]

Summary of Changes

Adds versioned (v20260427) list endpoints for internal transfers and cross-account transfers, mirroring the existing versioned list support for payments and recurring payments (commit e9274f9c).

Each affected GET list endpoint now routes through DateVersionedResponse: the default version continues to call the existing list() accessor, and version 20260427 calls a new list20260427() accessor. The 20260427 variant reuses the same model (the models already carry recurringTransferId / recurringCrossAccountTransferId); this change affects which records are returned, not the response shape, so no new model or Resources registration is required.

Jira: MC-15714

Public API Additions/Changes

New base-accessor methods (each @GatewayAPI / @API, throwing AccessorMethodNotImplementedException by default):

• TransferBaseAccessor#list20260427(TransferListOptions)
• RecurringTransferBaseAccessor#list20260427(RecurringTransferListOptions)
• CrossAccountTransferBaseAccessor#list20260427()
• CrossAccountRecurringTransferBaseAccessor#list20260427()

Versioned GET list endpoints (default → list(), version=20260427 → list20260427()):

• GET /users/{userId}/transfers
• GET /users/{userId}/recurring_transfers
• GET /users/{userId}/cross_account_transfers
• GET /users/{userId}/cross_account_transfers/recurring_cross_account_transfers

Controllers now accept an injected HttpServletRequest alongside any existing query parameters.

Downstream Consumer Impact

Non-breaking. Existing (default-version) clients are unaffected — they continue to hit the same list() accessor and receive identical responses. Accessor implementations that want the new behavior opt in by overriding list20260427(); until they do, requesting version=20260427 yields AccessorMethodNotImplementedException, consistent with the payments precedent.

How Has This Been Tested?

• ./gradlew check (JDK 21) — full build, all tests, coverage, and static analysis pass
• Targeted controller tests — 58/58 pass, including 4 new v20260427 tests (one per endpoint) verifying the versioned accessor is invoked for ...;version=20260427 and the default accessor for the unversioned media type
• Confirmed the annotation-processed gateway proxies regenerate with list20260427 for all four accessors

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works