Add a 'Flat Rate' option for each available UPS service

I would like to propose an enhancement for the Commerce UPS module that would greatly benefit users by providing more flexibility in how shipping rates are determined. Currently, the module integrates with the UPS API to calculate shipping costs dynamically. However, this does not accommodate scenarios where a fixed shipping rate is preferable.

This feature makes more sense when the feature to create UPS shipping labels is committed ✨ Add support for Shipping API, Label Shipping API and Void Shipping API Needs review .