8. Invoices Introduction: In invoices we are handling bidirectional synchronization that means we comparing any invoices which have changed since the last successful sync then pushing changes to the older invoice. Xero API supports the “If-modified-since” header parameter, which allows you to pull back only the records which are changed since the last successful sync. for this bidirectional sync we maintainedd a foreign key relationship between the invoice in our application and the one in Xero. we stored the InvoiceID…