[SC-73] multisig-transfer's cancel/reject need state-transition guard tests

[yusuftomilola]

Overview

cancel_transfer_request and reject_transfer_request (contracts/multisig-transfer/src/lib.rs) — worth tests confirming a request can't be cancelled or rejected after it's already been executed, and can't be double-rejected or double-cancelled.

Tasks

• Add a test attempting to cancel an already-execute_transfer'd request (should fail).
• Add a test attempting to reject an already-approved-and-executed request (should fail).
• Add a test double-cancelling or double-rejecting the same request.

Acceptance Criteria

• Post-execution cancel/reject, and double-cancel/double-reject, are all explicitly rejected and tested.

Notes for Contributors

Requires Rust + Soroban. Workspace: contracts/ (soroban-sdk 23, members: assetsup, contrib, multisig-wallet, multisig-transfer, asset-maintenance). Run cargo test --all, cargo fmt --all -- --check, and cargo clippy --all-targets --all-features -- -D warnings before opening a PR — CI enforces all three. Comment below to be assigned.

[cyberdocs120]

@cyberdocs120 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

I’d like to work on this issue because it addresses an important area of the project and presents a great opportunity to make a meaningful contribution. I’m particularly interested in delivering a solution that is reliable, maintainable, and aligned with the project’s existing architecture and development standards.

I have experience working across software development, including backend and frontend development, APIs, databases, testing, DevOps, and blockchain-based applications. I’m comfortable understanding existing codebases, identifying the root cause of issues, implementing clean and scalable solutions, and writing thorough tests to prevent regressions.

My approach would be to first understand the existing implementation and project conventions, then develop the solution in a focused and incremental way. I’ll ensure the changes are well-tested, documented where necessary, and do not introduce unnecessary complexity or break existing functionality. I’m also committed to clear communication, responding to review feedback, and delivering a polished contribution that provides real value to the project.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @cyberdocs120 to this issue.