[CT-03] Implement Escrow Release Validator with dispute window check in Rust

[devwums]

Problem

The payment_escrow contract has no explicit, independently-testable release validation function. Release logic is entangled with other contract state, making it impossible to unit test in isolation.

Proposed Solution

Create contracts/cntr/escrow_release.rs implementing pub fn validate_escrow_release(booking_status: &str, dispute_window_expired: bool) -> Result<(), &'static str>. Returns Ok(()) only when booking_status == "COMPLETED" AND dispute_window_expired == true. All implementation must live inside contracts/cntr/.

Acceptance Criteria

• File at contracts/cntr/escrow_release.rs
• Returns Err("Booking not completed") when status is not "COMPLETED"
• Returns Err("Dispute window still active") when dispute_window_expired is false
• Returns Ok(()) only when both conditions are met
• At least 5 unit tests covering all branches and combined conditions
• Compiles with cargo test

[Userhorlie]

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

I would love to take on this issue.

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

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[Userhorlie]

Resolved in PR #1044. Implementation lives in contracts/cntr/ with all acceptance criteria met and tests passing.

[Userhorlie]

Implemented in PR #1044. All acceptance criteria met, 26 unit tests passing.

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This issue has been completed by @Userhorlie as part of the Stellar Wave Program's 5th Wave 🥳

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