Feature request - allow customization of network failure behavior

[tmtrademarked]

Currently, in AvalaraTransaction#post_order/return_to_avalara, the method handles an error response by returning totalTax: 0.0. It would be great if there were a way for stores to customize this behavior. Perhaps having a configurable class like AvalaraErrorHandler which would be given the response object would make this simpler? That way, stores could replace the error handler with their own implementation as needed to create more advanced behaviors (like hooking into error reporting tools or raising errors or even implementing retries, etc).