Refactoring to use the new authentication package

[tombuildsstuff]

• Vendor the 0.1.1 / 0.2.0 tag once the PR's have been merged: https://github.com/hashicorp/go-azure-helpers/pulls
• Testing - blocked on the account

Once this is merged we should be able to add the documentation for Client Certificate authentication for both AzureRM and Azure Stack, and then flip on the feature-toggle

[katbyte]

LGTM 👍

[tombuildsstuff]

Tests look good:

$ acctests azurestack TestAccAzureStackResourceGroup_basic

=== RUN   TestAccAzureStackResourceGroup_basic
--- PASS: TestAccAzureStackResourceGroup_basic (61.22s)
PASS
ok  	github.com/terraform-providers/terraform-provider-azurestack/azurestack	61.646s

Provider seems fine in testing 👍

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. If you feel I made an error 🤖 🙉 , please reach out to my human friends 👉 [email protected]. Thanks!