Prevent issue_reputation self-rating and add SelfRating enforcement

[mikewheeleer]

Description

EscrowError::SelfRating is defined in types.rs but never used. issue_reputation checks caller == contract.client and freelancer == contract.freelancer, but does not explicitly prevent a degenerate contract where roles were migrated such that client and freelancer collapse to the same address from self-inflating reputation. Enforce the SelfRating guard.

Requirements and context

• Scoped to TalentTrust escrow Soroban contract (contracts/escrow).
• In issue_reputation, reject with EscrowError::SelfRating if contract.client == contract.freelancer (defense-in-depth alongside create-time InvalidParticipant).
• Confirm the guard interacts correctly with any future client-migration feature.
• Invariant: a single principal can never both issue and receive reputation on the same contract.
• Must be secure, tested, and documented.

Suggested execution

• Fork the repo and create a branch:
  • git checkout -b enhancement/reputation-self-rating-guard
• Implement changes:
  • contracts/escrow/src/lib.rs
  • Tests: contracts/escrow/src/test/reputation.rs
  • Docs: docs/escrow/REPUTATION.md
  • Include rustdoc/NatSpec-style doc comments on public functions
  • Validate security assumptions (auth, overflow, fail-closed state machine, storage TTL, fee accounting)

Test and commit

• Run tests: cargo test
• Cover edge cases (unauthorized callers, double release/refund, expired approvals, fee rounding, paused state)
• Include test output and security notes in the PR

Example commit message

feat(escrow): enforce SelfRating guard in issue_reputation

Guidelines

• Minimum 95% test coverage on new/changed code
• Clear documentation
• Timeframe: 96 hours from assignment

[victor62-art]

@victor62-art has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

studied the task at hand and i can say i have a clear understanding
pls assign me so i can begin implementation

ℹ️ Repo Maintainers: To accept this application, review their application or assign @victor62-art to this issue.

[drips-wave]

Congratulations, @victor62-art! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

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