Function to return workspace client on bundle.Bundle (#100)

Complementary command to check the identity in the context of a bundle
environment:

For example:
```
bricks bundle debug whoami -e development
```

bundle/bundle.go

@@ -3,13 +3,20 @@ package bundle
 import (
 	"context"
 	"path/filepath"
+	"sync"
 
 	"github.com/databricks/bricks/bundle/config"
 	"github.com/databricks/bricks/bundle/config/mutator"
+	"github.com/databricks/databricks-sdk-go/workspaces"
 )
 
 type Bundle struct {
 	Config config.Root
+
+	// Store a pointer to the workspace client.
+	// It can be initialized on demand after loading the configuration.
+	clientOnce sync.Once
+	client     *workspaces.WorkspacesClient
 }
 
 func (b *Bundle) MutateForEnvironment(env string) error {
@@ -51,3 +58,10 @@ func ConfigureForEnvironment(ctx context.Context, env string) (context.Context,
 
 	return Context(ctx, b), nil
 }
+
+func (b *Bundle) WorkspaceClient() *workspaces.WorkspacesClient {
+	b.clientOnce.Do(func() {
+		b.client = b.Config.Workspace.Client()
+	})
+	return b.client
+}

bundle/config/workspace.go

@@ -1,8 +1,53 @@
 package config
 
+import (
+	"github.com/databricks/databricks-sdk-go/databricks"
+	"github.com/databricks/databricks-sdk-go/workspaces"
+)
+
 // Workspace defines configurables at the workspace level.
 type Workspace struct {
-	// TODO: Add all unified authentication configurables.
+	// Unified authentication attributes.
+	//
+	// We omit sensitive attributes as they should never be hardcoded.
+	// They must be specified through environment variables instead.
+	//
+	// For example: token, password, Google credentials, Azure client secret, etc.
+	//
+
+	// Generic attributes.
 	Host    string `json:"host,omitempty"`
 	Profile string `json:"profile,omitempty"`
+
+	// Google specific attributes.
+	GoogleServiceAccount string `json:"google_service_account,omitempty"`
+
+	// Azure specific attributes.
+	AzureResourceID  string `json:"azure_workspace_resource_id,omitempty"`
+	AzureUseMSI      bool   `json:"azure_use_msi,omitempty"`
+	AzureClientID    string `json:"azure_client_id,omitempty"`
+	AzureTenantID    string `json:"azure_tenant_id,omitempty"`
+	AzureEnvironment string `json:"azure_environment,omitempty"`
+	AzureLoginAppID  string `json:"azure_login_app_id,omitempty"`
+}
+
+func (w *Workspace) Client() *workspaces.WorkspacesClient {
+	config := databricks.Config{
+		// Generic
+		Host:    w.Host,
+		Profile: w.Profile,
+
+		// Google
+		GoogleServiceAccount: w.GoogleServiceAccount,
+
+		// Azure
+		AzureResourceID:  w.AzureResourceID,
+		AzureUseMSI:      w.AzureUseMSI,
+		AzureClientID:    w.AzureClientID,
+		AzureTenantID:    w.AzureTenantID,
+		AzureEnvironment: w.AzureEnvironment,
+		AzureLoginAppID:  w.AzureLoginAppID,
+	}
+
+	return workspaces.New(&config)
 }

cmd/bundle/debug/debug.go

@@ -0,0 +1,15 @@
+package debug
+
+import (
+	"github.com/spf13/cobra"
+
+	parent "github.com/databricks/bricks/cmd/bundle"
+)
+
+var debugCmd = &cobra.Command{
+	Use: "debug",
+}
+
+func init() {
+	parent.AddCommand(debugCmd)
+}

cmd/bundle/debug/whoami.go

@@ -0,0 +1,30 @@
+package debug
+
+import (
+	"fmt"
+
+	"github.com/databricks/bricks/bundle"
+	parent "github.com/databricks/bricks/cmd/bundle"
+	"github.com/spf13/cobra"
+)
+
+var whoamiCmd = &cobra.Command{
+	Use: "whoami",
+
+	PreRunE: parent.ConfigureBundle,
+	RunE: func(cmd *cobra.Command, args []string) error {
+		ctx := cmd.Context()
+		w := bundle.Get(ctx).WorkspaceClient()
+		user, err := w.CurrentUser.Me(ctx)
+		if err != nil {
+			return err
+		}
+
+		fmt.Fprintln(cmd.OutOrStdout(), user.UserName)
+		return nil
+	},
+}
+
+func init() {
+	debugCmd.AddCommand(whoamiCmd)
+}

cmd/bundle/validate.go

@@ -7,7 +7,7 @@ import (
 	"github.com/spf13/cobra"
 )
 
-var validate = &cobra.Command{
+var validateCmd = &cobra.Command{
 	Use:   "validate",
 	Short: "Validate configuration",
 
@@ -24,5 +24,5 @@ var validate = &cobra.Command{
 }
 
 func init() {
-	AddCommand(validate)
+	AddCommand(validateCmd)
 }

main.go

@@ -3,6 +3,7 @@ package main
 import (
 	_ "github.com/databricks/bricks/cmd/api"
 	_ "github.com/databricks/bricks/cmd/bundle"
+	_ "github.com/databricks/bricks/cmd/bundle/debug"
 	_ "github.com/databricks/bricks/cmd/configure"
 	_ "github.com/databricks/bricks/cmd/fs"
 	_ "github.com/databricks/bricks/cmd/init"