+per #15327 Add AtLeastOnceDelivery trait

* also remove final of around methods, and let deliver send when not recoveryRunning

(cherry picked from commit 312b0d107a179accaf135f64ed9c3b78f3e351d1)

akka-docs/rst/scala/code/docs/persistence/PersistenceDocSpec.scala

@@ -9,7 +9,6 @@ import akka.persistence._
 
 import scala.concurrent.duration._
 import scala.language.postfixOps
-
 trait PersistenceDocSpec {
   val config =
     """
@@ -133,6 +132,48 @@ trait PersistenceDocSpec {
     }
   }
 
+  new AnyRef {
+    //#at-least-once-example
+    import akka.actor.{ Actor, ActorPath, Props }
+    import akka.persistence.AtLeastOnceDelivery
+
+    case class Msg(deliveryId: Long, s: String)
+    case class Confirm(deliveryId: Long)
+
+    sealed trait Evt
+    case class MsgSent(s: String) extends Evt
+    case class MsgConfirmed(deliveryId: Long) extends Evt
+
+    class MyPersistentActor(destination: ActorPath)
+      extends PersistentActor with AtLeastOnceDelivery {
+
+      def receiveCommand: Receive = {
+        case s: String           => persist(MsgSent(s))(updateState)
+        case Confirm(deliveryId) => persist(MsgConfirmed(deliveryId))(updateState)
+      }
+
+      def receiveRecover: Receive = {
+        case evt: Evt => updateState(evt)
+      }
+
+      def updateState(evt: Evt): Unit = evt match {
+        case MsgSent(s) =>
+          deliver(destination, deliveryId => Msg(deliveryId, s))
+
+        case MsgConfirmed(deliveryId) => confirmDelivery(deliveryId)
+      }
+    }
+
+    class MyDestination extends Actor {
+      def receive = {
+        case Msg(deliveryId, s) =>
+          // ...
+          sender() ! Confirm(deliveryId)
+      }
+    }
+    //#at-least-once-example
+  }
+
   new AnyRef {
     //#channel-example
     import akka.actor.{ Actor, Props }