Add new `connection` endpoints

[daffron]

SDK you're using (please complete the following information):

• Version 4.33.0

Is your feature request related to a problem? Please describe. New endpoints for managing connections have been released. https://developer.xero.com/documentation/guides/oauth2/tenants/#check-the-tenants-youre-authorised-to-access

Describe the solution you'd like These should be accessible via the SDK methods

Describe alternatives you've considered N/A

Additional context Im happy to raise a PR for this, just unsure what API to put this under, appStoreApi?