Support deletion of old events and snapshots

[xirc]

Features

• Support Akka Persistence Cassandra (https://doc.akka.io/docs/akka-persistence-cassandra/1.0.5/index.html) as the target journal and snapshot plugins.
• This deletion feature is an opt-in feature (disabled is the default) since it only supports the Akka Persistence Cassandra.
• akka-entity-replication deletes old events and snapshots automatically (when it saves events or snapshots)
• akka-entity-replication doesn't delete tagged events (tag_view):
  • Tagged events will be deleted using the Cassandra compaction strategy TimeWindowCompactionStrategy

Implementations

• Using deleteMessages and deleteSnapshots APIs:
  • deleteMessages: https://doc.akka.io/docs/akka/2.6.17/persistence.html#message-deletion
  • deleteSnapshots: https://doc.akka.io/docs/akka/2.6.17/persistence.html#snapshot-deletion