message: squash: const member variables
diff: @@ -40,15 +40,15 @@ private:
  static std::string replaceEnv(const std::string& attachment_template);
  // The name of the squash server cluster.
  - std::string cluster_name_;
  + const std::string cluster_name_;
  // The attachment body sent to squash server on create attachment.
  - std::string attachment_json_;
  + const std::string attachment_json_;
  // The total amount of time for an attachment to reach a final state (attached or error).
  - std::chrono::milliseconds attachment_timeout_;
  + const std::chrono::milliseconds attachment_timeout_;
  // How frequently should we poll the attachment state with the squash server.
  - std::chrono::milliseconds attachment_poll_period_;
  + const std::chrono::milliseconds attachment_poll_period_;
  // The timeout for individual requests to the squash server.
  - std::chrono::milliseconds request_timeout_;
  + const std::chrono::milliseconds request_timeout_;
  // Defines the pattern for interpolating environment variables in to the attachment.
  const static std::regex ENV_REGEX;
  @@ -68,8 +68,8 @@ public:
  void onFailure(Http::AsyncClient::FailureReason f) override { on_fail_(f); }
  private:
  - std::function<void(Http::ResponseMessagePtr&&)> on_success_;
  - std::function<void(Http::AsyncClient::FailureReason)> on_fail_;
  + const std::function<void(Http::ResponseMessagePtr&&)> on_success_;
  + const std::function<void(Http::AsyncClient::FailureReason)> on_fail_;
  };
  class SquashFilter : public Http::StreamDecoderFilter,
  