Eventlog compaction #136
Description
To avoid unbounded growth of mutation eventlog, a relatively simple strategy is log compaction.
Will be unlocked by #254
Old notes
The idea is that a new mutation log event for a given key would drop previous event for the same key. Log compaction would most likely happen during write of a new mutation log event.
The key could be determined by letting the app dev implementing a key callback function in the mutation definition.