Attribute Terraform API requests the CLI (#1598)

## Changes
This PR adds cli to the user agent sent downstream to the databricks
terraform provider when invoked via DABs.
 
## Tests
Unit tests. Based on the comment here
(https://github.com/databricks/cli/blob/10fe02075fec0b2e18d2eacf7412816d6e81d6bc/bundle/config/mutator/verify_cli_version_test.go#L113)
we don't need to set the version to make the test assertion work
correctly. This is likely because we use `go test` to run the tests
while the CLI is compiled and the version is set via `goreleaser`.

bundle/deploy/terraform/init.go

@@ -15,6 +15,7 @@ import (
 	"github.com/databricks/cli/bundle"
 	"github.com/databricks/cli/bundle/config"
 	"github.com/databricks/cli/bundle/internal/tf/schema"
+	"github.com/databricks/cli/internal/build"
 	"github.com/databricks/cli/libs/diag"
 	"github.com/databricks/cli/libs/env"
 	"github.com/databricks/cli/libs/log"
@@ -219,8 +220,10 @@ func setProxyEnvVars(ctx context.Context, environ map[string]string, b *bundle.B
 }
 
 func setUserAgentExtraEnvVar(environ map[string]string, b *bundle.Bundle) error {
-	var products []string
-
+	// Add "cli" to the user agent in set by the Databricks Terraform provider.
+	// This will allow us to attribute downstream requests made by the Databricks
+	// Terraform provider to the CLI.
+	products := []string{fmt.Sprintf("cli/%s", build.GetInfo().Version)}
 	if experimental := b.Config.Experimental; experimental != nil {
 		if experimental.PyDABs.Enabled {
 			products = append(products, "databricks-pydabs/0.0.0")

bundle/deploy/terraform/init_test.go

@@ -262,10 +262,9 @@ func TestSetUserAgentExtraEnvVar(t *testing.T) {
 
 	env := make(map[string]string, 0)
 	err := setUserAgentExtraEnvVar(env, b)
-
 	require.NoError(t, err)
 	assert.Equal(t, map[string]string{
-		"DATABRICKS_USER_AGENT_EXTRA": "databricks-pydabs/0.0.0",
+		"DATABRICKS_USER_AGENT_EXTRA": "cli/0.0.0-dev databricks-pydabs/0.0.0",
 	}, env)
 }