Add support for Shipping API, Label Shipping API and Void Shipping API

Hi, I'm the maintainer of the Commerce Shipping Label module. Please let me know if you need any help integrating with it. The module currently only works with Commerce EasyPost, but we're using that combination in production without any issues. I'm confident recommending it for other modules to adopt.

Commerce Shipping Label provides you with a user interface for generating a remote shipment and optionally scheduling a pickup. (It's an extension of the current Shipments tab on an order.) It also provides the storage for the label files and customs documents. There's a submodule that integrates with Zebra Browser Print (https://developer.zebra.com/products/printers/browser-print), that allows you to print ZPL files to a connected printer directly from the Drupal web interface.

If you were to adopt Commerce Shipping Label as a base, you would only need to implement some interfaces that it provides, and you could focus on the UPS API rather than doing all that user interface work. The interfaces that are there now were designed to work with EasyPost, so please let me know if they are incompatible with how the UPS API works in some way. I'm sure we can adjust them to work.

The merge request adds initial support for creating UPS Shipping Labels. It introduces basic functionality for generating these labels and includes a dependency on the Commerce Shipping Label API module to aid integration and manage label operations efficiently.

Can the module maintainers confirm if it's okay to add a dependency on the Commerce Shipping Label API module before I continue development?

Very interested in this.