Integrate Gusto Embedded Payroll into an SMB platform and process off-cycle contractor payments

Steps

1. Obtain a system access token using client_credentials, then create a partner-managed company via POST /v1/partner_managed_companies
2. Add the contractor to the company using the Gusto contractor creation endpoint, providing name, SSN or EIN, and payment method
3. Create an off-cycle payroll using the Gusto payroll endpoints specifying off_cycle: true and the pay period dates
4. Add contractor payment line items to the off-cycle payroll with the appropriate payment amount and earnings type
5. Submit the off-cycle payroll for processing via the payroll submission endpoint; confirm the pay date is at least the minimum number of business days in the future for ACH processing
6. Poll the payroll status endpoint or listen for Gusto webhooks to confirm processing and catch any rejections (e.g., insufficient bank balance, invalid routing number)