code: func validateKeyArgs(keyName string, targetDir string) error {
  	if !validKeyName(keyName) {
  		return fmt.Errorf("key name \"%s\" must start with lowercase alphanumeric characters and can include \"-\" or \"_\" after the first character", keyName)
  	}
  
  	pubKeyFileName := keyName + ".pub"
  	if _, err := os.Stat(targetDir); err != nil {
  		return fmt.Errorf("public key path does not exist: \"%s\"", targetDir)
  	}
  	targetPath := filepath.Join(targetDir, pubKeyFileName)
  	if _, err := os.Stat(targetPath); err == nil {
  		return fmt.Errorf("public key file already exists: \"%s\"", targetPath)
  	}
  	return nil
  }
docs: // validate that all of the key names are unique and are alphanumeric + _ + -
  // and that we do not already have public key files in the target dir on disk