1.8.0
This PR introduces the ability to request, receive, and manage a token from Xero API using the client credentials auth method.
Implements OA2's client_credentials grant supported by Xero's Custom Connection feature 🥳
https://developer.xero.com/documentation/guides/oauth2/custom-connections/
This enables developers to create machine to machine interactions for a single Xero org.
Fixed Budgets endpoints - added budget balances and budget lines to serialize correctly.