Persist the state of the MessageGroups [INT-2155]

[spring-operator]

Oleg Zhurakousky opened INT-2155 and commented

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This issue is a sub-task of #6135

[spring-operator]

Oleg Zhurakousky commented

Currently, when Messages are stored as part of the MessageGroup various implementations of the MessageGroupStore only persist the relationship between the MessageGroup and individual Messages. With the refactoring effort described by various sub-tasks of #6135 MessageGrouStore will have more attributes describing its state than just the relationship (e.g., timestamp, complete etc.) so we need to make sure that this is persisted as well.