Configure Terraform provider auth through env vars (#290)

## Changes

Auth relied on setting a profile. In this change we enumerate all
configuration properties and export all non-empty ones as a map with
environment variables. We then pass this map to the Terraform execution
wrapper.

This results in Terraform using the bundle's authentication
configuration.

This change is needed to make #287 work.

## Tests

Manually.

bundle/bundle.go

@@ -17,6 +17,7 @@ import (
 	"github.com/databricks/bricks/libs/git"
 	"github.com/databricks/bricks/libs/locker"
 	"github.com/databricks/databricks-sdk-go"
+	sdkconfig "github.com/databricks/databricks-sdk-go/config"
 	"github.com/hashicorp/terraform-exec/tfexec"
 )
 
@@ -127,3 +128,34 @@ func (b *Bundle) GitRepository() (*git.Repository, error) {
 
 	return git.NewRepository(rootPath)
 }
+
+// AuthEnv returns a map with environment variables and their values
+// derived from the workspace client configuration that was resolved
+// in the context of this bundle.
+//
+// This map can be used to configure authentication for tools that
+// we call into from this bundle context.
+func (b *Bundle) AuthEnv() (map[string]string, error) {
+	if b.client == nil {
+		return nil, fmt.Errorf("workspace client not initialized yet")
+	}
+
+	cfg := b.client.Config
+	out := make(map[string]string)
+	for _, attr := range sdkconfig.ConfigAttributes {
+		// Ignore profile so that downstream tools don't try and reload
+		// the profile even though we know the current configuration is valid.
+		if attr.Name == "profile" {
+			continue
+		}
+		if len(attr.EnvVars) == 0 {
+			continue
+		}
+		if attr.IsZero(cfg) {
+			continue
+		}
+		out[attr.EnvVars[0]] = attr.GetString(cfg)
+	}
+
+	return out, nil
+}

bundle/deploy/terraform/convert.go

@@ -52,7 +52,6 @@ func convPermission(ac resources.Permission) schema.ResourcePermissionsAccessCon
 func BundleToTerraform(config *config.Root) *schema.Root {
 	tfroot := schema.NewRoot()
 	tfroot.Provider = schema.NewProviders()
-	tfroot.Provider.Databricks.Profile = config.Workspace.Profile
 	tfroot.Resource = schema.NewResources()
 
 	for k, src := range config.Resources.Jobs {

bundle/deploy/terraform/init.go

@@ -6,6 +6,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strings"
 
 	"github.com/databricks/bricks/bundle"
 	"github.com/databricks/bricks/bundle/config"
@@ -14,6 +15,7 @@ import (
 	"github.com/hashicorp/hc-install/product"
 	"github.com/hashicorp/hc-install/releases"
 	"github.com/hashicorp/terraform-exec/tfexec"
+	"golang.org/x/exp/maps"
 )
 
 type initialize struct{}
@@ -89,6 +91,18 @@ func (m *initialize) Apply(ctx context.Context, b *bundle.Bundle) ([]bundle.Muta
 		return nil, err
 	}
 
+	env, err := b.AuthEnv()
+	if err != nil {
+		return nil, err
+	}
+
+	// Configure environment variables for auth for Terraform to use.
+	log.Debugf(ctx, "Environment variables for Terraform: %s", strings.Join(maps.Keys(env), ", "))
+	err = tf.SetEnv(env)
+	if err != nil {
+		return nil, err
+	}
+
 	b.Terraform = tf
 	return nil, nil
 }