DDSIRTP21 — Include key in serialized ParticipantMessageData

The specification states in section 9.6.2.1 that the key portion of ParticipantMessageData is not serialized as part of the DATA submessage. The stated argument is that the key is already part of the DATA submessage. This argument is incorrect, the DATA message may optionally include a KeyHash which is not necessarily the same as the key. Moreover this makes the ParticipantMessageData special in the way it is serialized. The saving in bandwidth consumed do not justify all this "special code". It would be far better if the ParticipantMessageData was treated as any regular data message and the key was serialized along.
Resolution:
Change the description in Section 9.6.2.1 to not refrain from serializing the key of ParticipantMessageData.

Change the description in Section 9.6.2.1 to not refrain from serializing the key of ParticipantMessageData.