Expose contact sales default values

[lrakauskas]

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

• Version 12.0.1

Is your feature request related to a problem? Please describe.
Unable to retrieve most of contact's "Sales Defaults" values.

Describe the solution you'd like
Package/API already exposes things like SalesDefaultAccountCode or SalesDefaultLineAmountType, but there's a lot of other fields that are configurable on Xero dashboard that are not exposed via API (see screenshot). Could this be added? I'm particularly interested in "Credit limit" & "Block new invoices when credit limit is reached"

Describe alternatives you've considered
N/A

Additional context
N/A

[github-actions]

PETOSS-947

[github-actions]

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