Added INS option to ShipmentOptions

[WeTurkstra]

Description

Added the INS option to the shipping options.

Motivation and context

I want to be able to create shipments with an insurance amount added.

How has this been tested?

Extended the unit tests for the shipment options.

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

Go over all the following points, and put an x in all the boxes that apply.

Please, please, please, don't send your pull request until all of the boxes are ticked.

• [x] I have read the CONTRIBUTING document.
• [x] My pull request addresses exactly one patch/feature.
• [x] I have created a branch for this patch/feature.
• [x] Each individual commit in the pull request is meaningful.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.
• [x] If my change requires a change to the documentation, I have updated it accordingly.
• [x] My code follows the code style of this project.