[apache#26644] Set GCS UserAgent to Beam for Go. (apache#26702)

* [apache#26644] Set GCS UserAgent to Beam.

* Wrap agent in parens.

---------

Co-authored-by: lostluck <13907733+lostluck@users.noreply.github.com>

sdks/go/pkg/beam/io/filesystem/gcs/gcs.go

@@ -31,7 +31,6 @@ import (
 	"github.com/apache/beam/sdks/v2/go/pkg/beam/util/fsx"
 	"github.com/apache/beam/sdks/v2/go/pkg/beam/util/gcsx"
 	"google.golang.org/api/iterator"
-	"google.golang.org/api/option"
 )
 
 func init() {
@@ -46,11 +45,11 @@ type fs struct {
 // default credentials. If it fails, it falls back to unauthenticated
 // access.
 func New(ctx context.Context) filesystem.Interface {
-	client, err := storage.NewClient(ctx, option.WithScopes(storage.ScopeReadWrite))
+	client, err := gcsx.NewClient(ctx, storage.ScopeReadWrite)
 	if err != nil {
 		log.Warnf(ctx, "Warning: falling back to unauthenticated GCS access: %v", err)
 
-		client, err = storage.NewClient(ctx, option.WithoutAuthentication())
+		client, err = gcsx.NewUnauthenticatedClient(ctx)
 		if err != nil {
 			panic(errors.Wrapf(err, "failed to create GCS client"))
 		}

sdks/go/pkg/beam/util/gcsx/gcs.go

@@ -28,15 +28,19 @@ import (
 	"google.golang.org/api/option"
 )
 
+var userAgent = option.WithUserAgent("(GPN:Beam)")
+
 // NewClient creates a new GCS client with default application credentials, and supplied
 // OAuth scope. The OAuth scopes are defined in https://pkg.go.dev/cloud.google.com/go/storage#pkg-constants.
+// Sets the user agent to Beam.
 func NewClient(ctx context.Context, scope string) (*storage.Client, error) {
-	return storage.NewClient(ctx, option.WithScopes(scope))
+	return storage.NewClient(ctx, option.WithScopes(scope), userAgent)
 }
 
 // NewUnauthenticatedClient creates a new GCS client without authentication.
+// Sets the user agent to Beam.
 func NewUnauthenticatedClient(ctx context.Context) (*storage.Client, error) {
-	return storage.NewClient(ctx, option.WithoutAuthentication())
+	return storage.NewClient(ctx, option.WithoutAuthentication(), userAgent)
 }
 
 // Upload writes the given content to GCS. If the specified bucket does not