Added Databricks CLI & Azure CLI authentication and a basic integration test

[nfx]

No description provided.

[zacdav-db]

should this be removed?

[nfx]

Nope. It holds private state used for token refreshing internally when it's about to expire

[zacdav-db]

Need to fix is_<cloud> functions to handle NULL:

databricks-sdk-r/R/api_client.R

Lines 123 to 135 in bb96aac

	is_azure <- function() {
	grepl(".azuredatabricks.net", cfg$host)
	}
	# is_gcp returns true if client is configured for GCP
	is_gcp <- function() {
	grepl(".gcp.databricks.com", cfg$host)
	}
	# is_aws returns true if client is configured for AWS
	is_aws <- function() {
	!is_azure() & !is_gcp()
	}

e.g.

is_azure <- function() {
  if (!is.null(cfg$host)) {
    grepl(".azuredatabricks.net", cfg$host)
  } else {
    FALSE
  }
}

[nfx]

That's a bit irrelevant to this PR, can you please send one?

[nfx]

also, in this case, we won't have null there, per se