[FEATURE] Migrate to new unique databricks hostnames

[sdebruyn]

Is your feature request related to a problem? Please describe.
Currently not a problem, but it's advised to start using the new unique URLs for each Databricks workspace as documented in https://docs.microsoft.com/en-us/azure/databricks/release-notes/product/2020/april#unique-urls-for-each-azure-databricks-workspace

Describe the solution you'd like
Replace the current code that uses https://.azuredatabricks.net/

Additional context
The current hostnames have not been deprecated (yet) so we have still time.

[sdebruyn]

Tracked in the azurerm provider in hashicorp/terraform-provider-azurerm#6732

[nfx]

@sdebruyn we'll look into this issue and see what we can do. this is not a complicated one.

[lawrencegripper]

Created a PR here to add into AzureRM: hashicorp/terraform-provider-azurerm#6973

[stikkireddy]

@lawrencegripper also noticed that in the existing code I actually can get the url with the GET request from the management API so, we may not need the workspace url fetched from the Azure RM client as the management api provides a url with the new format.

The following get request provides it:

https://management.azure.com/subscriptions/" + a.TokenPayload.SubscriptionID + "/resourceGroups/" + a.TokenPayload.ResourceGroup + "/providers/Microsoft.Databricks/workspaces/" + a.TokenPayload.WorkspaceName + "" +
		"?api-version=2018-04-01

[lawrencegripper]

Ah nice work around, in good news the change is shipping now from azurerm so can be used shortly if that saves some effort hashicorp/terraform-provider-azurerm#6732

[stuartleeks]

Just shipped 😀

https://github.com/terraform-providers/terraform-provider-azurerm/releases/tag/v2.11.0

[EliiseS]

I'll be picking up this with @lawrencegripper in an attempt that it'll fix #92