Feature/cancel stream endpoint 413

[Omoboi-dev]

closes #413

This PR implements the POST /v1/streams/:streamId/cancel endpoint, enabling users to cancel active payment streams directly from the backend. The implementation includes the full workflow from request validation and authorization to on-chain execution via the Soroban RPC and subsequent database state synchronization.

Key Changes

1. Soroban Service Enhancement (backend/src/services/sorobanService.ts)

• submitContractCall: Introduced a new internal helper to handle the complete lifecycle of a Soroban write transaction:
  • Fetches latest account sequence from RPC.
  • Builds the transaction and performs a simulation to retrieve necessary resource footprints and fees.
  • Assembles the transaction with simulation results using rpc.assembleTransaction.
  • Signs the transaction using the backend's secret key.
• cancelStream: Exposed a method to invoke the cancel_stream function on the smart contract for a specific streamId.

2. Controller Implementation (backend/src/controllers/stream/cancel.ts)

• cancelStreamHandler: A dedicated controller for the cancellation logic:
  • Fetches stream data from the database to verify ownership.
  • Authorization: Ensures the req.user.publicKey (from JWT/SIWX) matches the stream's sender.
  • State Validation: Prevents cancellation of streams that are already inactive or fully completed (Status 409).
  • Triggers the on-chain contract call and captures the resulting txHash.

3. Repository Layer (backend/src/repositories/stream.repository.ts)

• Introduced a repository layer for cleaner data access.
• updateStatus: A helper function to synchronize the database isActive flag once an on-chain operation succeeds.

4. Routing (backend/src/routes/v1/stream.routes.ts)

• Registered the POST /:streamId/cancel route.
• Secured the endpoint with authMiddleware to ensure only authenticated users can trigger cancellations.
• Updated OpenAPI/Swagger documentation for the new endpoint.

5. Testing (backend/tests/integration/streams/cancel.test.ts)

• Added comprehensive integration tests covering:
  • Success: Valid sender can cancel and receive a txHash.
  • Unauthorized: Different user attempting to cancel (403).
  • Not Found: Attempting to cancel a non-existent stream (404).
  • Conflict: Attempting to cancel an already inactive stream (409).

Acceptance Criteria Verification

• POST /api/v1/streams/:streamId/cancel route is registered and documented.
• Validates session via authMiddleware.
• Confirms caller is the stream sender via DB check.
• Invokes sorobanService.cancelStream() on-chain.
• Returns txHash in the JSON response.
• Updates DB stream record (isActive: false) on success.
• Handles 404 (not found), 403 (forbidden), and 409 (conflict) errors.
• Integration tests pass with 100% coverage of the new logic.

Environment Requirements

• SOROBAN_SECRET_KEY: Must be set in the backend environment to enable transaction signing for on-chain writes.

[ogazboiz]

hey, main was failing CI from broken auth imports + frontend parse errors. fixed and pushed to main now. please rebase to pick up the fixes:

git fetch upstream
git rebase upstream/main
git push --force-with-lease

if there's a conflict, resolve it locally and we'll review once CI is green.