Use a third party tax service (OCC-62)

[sarahelsaig]

Part of #33, not part of the MVP.

The goal is to implement ITaxProvider using a third party tax service, the primary candidates are Avalara AvaTax, TaxJar and WooCommerce Tax. If you can recommend other services, please comment! Must already have a NuGet package. They above mentioned all have: Avalara.AvaTax, TaxJar, WooCommerceNET respectively.

Place the provider-specific parts into a separate project/feature.

Site Settings

In both cases you will need to provide some extra information.

• Login or API key in a provider-specific setting.
• Destination address is also needed. This may be shared by shipping so treat it as a setting not specific to this feature.

Jira issue

[MikeAlhayek]

Please watch this video https://www.youtube.com/watch?v=0aPtye5ba4A

This video shows how WooCommerce handles taxes. This maybe a good start. We may want to mimic these options as WooCommerce is already used by millions of online shopping carts and covers a most tax scenarios.