Major Description
Design considerations:
1) Create generic DDL custom discovery message pair - INIT and ACK messages - which will hold concrete DDL commands.
2) Originator must generate unique message ID to be able to track it later.
3) Coordinator calculates all participants through affinity API and adds them to message.
4) INIT message goes through the ring and:performs some fast preliminary checks if necessary and collects error; in particular it may verify whether schema change is valid to allow for fail-fast client notification.;
5) If at least one error occurs during INIT stage, originator may throw exception to the user.
6) ACK message schedules asynchronous execution of the command.