Implement an Avalara AvaTax nexus determination and tax calculation call with address validation and document commit for a checkout integration

Steps

1. POST /api/v2/addresses/resolve to validate and normalize the destination address before tax calculation; an invalid address returns error details and should block checkout or prompt correction
2. Build a CreateTransactionModel with type SalesOrder (not SalesInvoice until post-payment commit), customerCode, addresses (ShipFrom, ShipTo), and lines array with each line's amount, quantity, and taxCode
3. POST /api/v2/transactions/create and parse the response: totalTax is the aggregate; lines[].tax gives per-line breakdowns useful for cart display
4. After payment capture, call POST /api/v2/transactions/{code}/commit to change the document type to SalesInvoice and lock it for reporting — or create with type SalesInvoice and commit:true directly
5. For returns, create a ReturnInvoice transaction referencing the original invoice code so Avalara reverses the tax obligation correctly for filing purposes