Replace FlowMessage by TraceableMessage

[bitzl]

Flusswerk highly encourages the use of custom message implementations. As these were error prone, an abstract base class FlusswerkMessage was introduced, abstracting technical requirements. The idea was to make your implementation as safe and simple as possible without getting in your way.

To support tracing a processing flow there is a Message implementation FlowMessage. This class breaks the spirit in that it is a subclass of DefaultMessage and not an abstract technical base class anymore.

Solution

Deprecate/remove FlowMessage and Introduce TraceableMessage (here assuming #143 - removing id - is already implemented):

public abstract class TraceableMessage extends FlusswerkMessage {

  private final String tracingId;

  public TraceableMessage(String tracingId) {
    this.tracingId = tracingId;
  }

  public String getTracingId() {
    return tracingId;
  }

}

[bitzl]

Won't fix: Tracing is now part of Message itself.