mark older LeastShardAllocationStrategy as obsolete (#6975)

* mark older LeastShardAllocationStrategy as obsolete

* added API approvals

Author: Aaronontheweb

src/contrib/cluster/Akka.Cluster.Sharding/ClusterSharding.cs

@@ -1415,10 +1415,13 @@ public IShardAllocationStrategy DefaultShardAllocationStrategy(ClusterShardingSe
             }
             else
             {
+                // TODO: remove this in v1.6 and force all users to use only the new strategy going forward
                 // old algorithm
                 var threshold = settings.TuningParameters.LeastShardAllocationRebalanceThreshold;
                 var maxSimultaneousRebalance = settings.TuningParameters.LeastShardAllocationMaxSimultaneousRebalance;
+#pragma warning disable CS0618 // Type or member is obsolete
                 return new LeastShardAllocationStrategy(threshold, maxSimultaneousRebalance);
+#pragma warning restore CS0618 // Type or member is obsolete
             }
         }
     }

src/contrib/cluster/Akka.Cluster.Sharding/ShardAllocationStrategy.cs

@@ -139,6 +139,7 @@ public static IShardAllocationStrategy LeastShardAllocationStrategy(int absolute
     /// The number of ongoing rebalancing processes can be limited by `maxSimultaneousRebalance`.
     /// </summary>
     [Serializable]
+    [Obsolete("Use ShardAllocationStrategy.LeastShardAllocationStrategy instead. This will be removed in v1.6.")]
     public class LeastShardAllocationStrategy : AbstractLeastShardAllocationStrategy
     {
         private readonly int _rebalanceThreshold;

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterSharding.DotNet.verified.txt

@@ -180,6 +180,8 @@ namespace Akka.Cluster.Sharding
     {
         void Start();
     }
+    [System.ObsoleteAttribute("Use ShardAllocationStrategy.LeastShardAllocationStrategy instead. This will be re" +
+        "moved in v1.6.")]
     public class LeastShardAllocationStrategy : Akka.Cluster.Sharding.Internal.AbstractLeastShardAllocationStrategy
     {
         public LeastShardAllocationStrategy(int rebalanceThreshold, int maxSimultaneousRebalance) { }

src/core/Akka.API.Tests/verify/CoreAPISpec.ApproveClusterSharding.Net.verified.txt

@@ -180,6 +180,8 @@ namespace Akka.Cluster.Sharding
     {
         void Start();
     }
+    [System.ObsoleteAttribute("Use ShardAllocationStrategy.LeastShardAllocationStrategy instead. This will be re" +
+        "moved in v1.6.")]
     public class LeastShardAllocationStrategy : Akka.Cluster.Sharding.Internal.AbstractLeastShardAllocationStrategy
     {
         public LeastShardAllocationStrategy(int rebalanceThreshold, int maxSimultaneousRebalance) { }