code: func Scope(scopes ...string) Option {
  	return func(tok *Bearer) error {
  		if len(scopes) > 0 {
  			return Claim("scope", strings.Join(scopes, " "))(tok)
  		}
  		return nil
  	}
  }
docs: // Scope is an option that adds a Scope ("scope") field to generated tokens.
  // Scopes are joined with a space (" ") separator.