* lease api
* Cluster singleton manager with lease
* Refactor OldestData to use option for actor reference
* Sharding with lease
* Docs for singleton and sharding lease + config for sharding lease
* Have ddata shard wait until lease is acquired before getting state
So now we can compile akka-distributed-data with
-Xfatal-warnings - though I'm not yet sure about
enabling the (other) undisciplineScalacOptions
* Fix multi-node silencing
* Fix scaladoc warnings
* Introduce annotation to declare ccompat use
* Add explicit toString
* Fix deprecation on 2.13
* Move 'immutable' ccompat helpers to shared ccompat package
* Add MiMa for internal scala 2.13 compatibility class
* Internal API markers
* Fix scaladoc generation
Got bitten by https://github.com/scala/bug/issues/11021
* Avoid -Ywarn-unused:_ on Scala 2.13
* Exclude warn-unused:explicits when generating docs
* Don't apply discipline to the docs compilation run
This approach also means no explicit code is needed anymore to
prevent #26119 from being triggered.
