Use the Moov transfer-options endpoint to determine valid source and destination payment-method combinations before creating a multi-rail transfer

Steps

1. Call POST /accounts/{accountID}/transfer-options with an amount and source/destination account references to retrieve valid payment-method combinations, since not all source and destination pairings are valid on Moov
2. Filter available options by each account's enabled capabilities; a source account needs send-funds capability and a destination account needs collect-funds capability
3. Select the appropriate rail per use case from what's returned: bank accounts (same-day ACH, standard ACH, faster ACH as source), RTP or push-to-card as destination-only options, or Moov wallet-to-wallet transfers
4. Generate a deterministic X-Idempotency-Key, up to 36 characters with UUID v5 supported, and include it on every POST /transfers call to prevent duplicate transfers
5. Handle a 409 response on transfer creation as confirmation a transfer already exists for that idempotency key, rather than retrying with a new key
6. Account for Federal Reserve bank holidays in scheduling; transfers created on a holiday are processed the next business day, and card-sale settlement is delayed when the settlement day falls on one