`ForceCancelReasonHashMissing` (#34) is documented but never actually returned

[dinahmaccodes]

Tier: Easy
Description: force_cancel_shipment (lib.rs:4340-4356) validates its reason hash via the generic validation::validate_hash(), which returns InvalidHash for an all-zero hash — never the dedicated variant. Compare resolve_dispute (lib.rs:4882-4885), which has an inline comment explaining it uses a specific error rather than the generic one, and correctly returns DisputeReasonHashMissing.
Files: contracts/shipment/src/errors.rs:84, contracts/shipment/src/error_map.rs:249, 540, contracts/shipment/src/lib.rs:4340-4356
Tasks:

• Make force_cancel_shipment return ForceCancelReasonHashMissing for a missing/zero reason hash, following the resolve_dispute pattern
  Acceptance Criteria:
• ForceCancelReasonHashMissing is actually returned by the code path it was designed for

[aliyuzuliehat25]

@aliyuzuliehat25 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi, I’d like to work on this issue.

I’ll review the existing force_cancel_shipment implementation and compare it with the resolve_dispute validation pattern to make the smallest focused change.

Proposed approach

• Update force_cancel_shipment so a missing/all-zero reason hash is explicitly detected before the generic validate_hash() call.
• Return ForceCancelReasonHashMissing for that specific invalid input.
• Follow the established resolve_dispute pattern and preserve the existing behavior for other invalid hashes.
• Avoid unrelated refactoring.

Test strategy
I’ll add focused regression coverage verifying that:

• A zero/missing reason hash returns ForceCancelReasonHashMissing.
• A valid reason hash succeeds as before.
• Other invalid hash inputs continue to return the appropriate generic validation error.
• Existing force_cancel_shipment behavior remains unchanged.

Validation
I’ll run the focused shipment contract tests, formatting/lint/build checks, and applicable repository CI checks.

Estimate
I estimate a few hours to 1 day for implementation and validation.

I’ll wait for assignment before starting.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @aliyuzuliehat25 to this issue.

[feyibosslady]

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

Hi maintainer

I'm a software engineer with experience across both frontend and backend development, working with Go, Python, JavaScript, and TypeScript.

I have a strong foundation in Go for backend services, hands-on experience with Python for scripting and infrastructure tooling, and solid working knowledge of JavaScript and TypeScript for frontend and full-stack development. I care about writing clean, maintainable code and think about how changes affect deployment and testing pipelines, not just the immediate fix.

I've gone through the issue and I'm confident I can deliver a solid solution.

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

[Aisha000-0]

@Aisha000-0 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hello maintainer I can fix this issue

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Aisha000-0 to this issue.