Feat: adds support for live-rates, service-groups, packingslip, and user-parcel-templates endpoints

[macder]

adds support for the the following endpoints:

• https://api.goshippo.com/live-rates/
• https://api.goshippo.com/service-groups/
• https://api.goshippo.com/orders/<order-object-id>/packingslip/
• https://api.goshippo.com/user-parcel-templates/

[sonarcloud[bot]]

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