LogDog: Implement prefix registration in Butler.

client/internal/logdog/butler/butler.go

Index: client/internal/logdog/butler/butler.go
diff --git a/client/internal/logdog/butler/butler.go b/client/internal/logdog/butler/butler.go
index 8b0684a451f56183d2a0f2ab7153d2473970aba6..ef5d5899c8ba06e52b23674717735ef56090088b 100644
--- a/client/internal/logdog/butler/butler.go
+++ b/client/internal/logdog/butler/butler.go
@@ -52,9 +52,6 @@ type Config struct {
 	Project config.ProjectName
 	// Prefix is the log stream common prefix value.
 	Prefix types.StreamName
-	// Secret is the prefix secret that will be used for streams generated by this
-	// Butler.
-	Secret types.PrefixSecret
 
 	// BufferLogs, if true, instructs the butler to buffer collected log data
 	// before sending it to Output.
@@ -88,9 +85,6 @@ func (c *Config) Validate() error {
 	if err := c.Prefix.Validate(); err != nil {
 		return fmt.Errorf("invalid prefix: %v", err)
 	}
-	if err := c.Secret.Validate(); err != nil {
-		return fmt.Errorf("invalid secret: %v", err)
-	}
 	return nil
 }
 
@@ -154,7 +148,6 @@ func New(ctx context.Context, config Config) (*Butler, error) {
 		Clock:            clock.Get(ctx),
 		Project:          config.Project,
 		Prefix:           config.Prefix,
-		Secret:           config.Secret,
 		MaxBufferedBytes: streamBufferSize,
 		MaxBundleSize:    config.Output.MaxSize(),
 	}