[CT-01] Implement submit_document handler

[mftee]

Problem

The POST /submit endpoint in the Rust service returns a hardcoded BAD_REQUEST with not yet implemented. Documents submitted through this route are never anchored on Stellar, making the submission flow non-functional.

Proposed Solution

Implement the submit_document handler inside contract/module/submit/. The implementation must call the existing StellarClient to anchor the document hash and persist the submission record in Redis.

Acceptance Criteria

• Handler validates that the document_hash is a valid 64-character lowercase hex string using HashValidator::validate_sha256
• Calls StellarClient::anchor_hash() with the document hash
• On successful anchoring, stores the submission record in Redis under key submit:{document_hash} with fields: document_id, submitter, txHash, and anchored_at (Unix timestamp)
• Returns 200 with a SubmitResponse containing success=true, transaction_id, and anchored_at
• Returns 400 for invalid hash format with a descriptive error message
• Returns 409 Conflict if the hash has already been submitted (key already exists in Redis)
• Implementation files live inside contract/module/submit/

[shadrach68]

@shadrach68 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hi maintainer, I'd like to work on this issue. Can you assign?

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[dotmantissa]

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

Hi 👋 I'm a full-stack developer
I will love to work on this issue please assign.

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[Auwal007]

@Auwal007 has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

I can replace that hardcoded stub with the full submission pipeline. I'll drop in the HashValidator check first to fail fast with a 400, add an existential Redis query to trigger the 409 Conflict for duplicates, and then coordinate the StellarClient anchoring with the final multi-field Redis write. I've built high-throughput async data ingestion services in Rust before, so I'll make sure the error propagation is completely airtight.

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[Jumongweb]

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

Hi maintainer, i will like to solve this issue

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[Tyler7x]

@Tyler7x has applied to work on this issue as part of the Stellar Wave Program's 5th wave.

Hey maintainers,

I’d be happy to take this one.

I’ve looked through the issue and it seems straightforward enough to implement cleanly while keeping things consistent with the existing code. I’ll make sure it’s solid and properly tested.

Let me know if I can pick it up.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Tyler7x to this issue.

[drips-wave]

Congratulations, @Tyler7x! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 2, 2026.

🧑‍💻 @Tyler7x: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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