Fix unassignedShards metric and rename singletons metric tag (#123)

* Fix metrics

* Change order

Author: ghostdogpr

entities/src/main/scala/com/devsisters/shardcake/Sharding.scala

@@ -68,7 +68,7 @@ class Sharding private (
           ZIO.foreach(singletons) {
             case (name, run, None) =>
               ZIO.logDebug(s"Starting singleton $name") *>
-                Metrics.singletons.tagged("name", name).increment *>
+                Metrics.singletons.tagged("singleton_name", name).increment *>
                 run.forkDaemon.map(fiber => (name, run, Some(fiber)))
             case other             => ZIO.succeed(other)
           }
@@ -83,7 +83,7 @@ class Sharding private (
           ZIO.foreach(singletons) {
             case (name, run, Some(fiber)) =>
               ZIO.logDebug(s"Stopping singleton $name") *>
-                Metrics.singletons.tagged("name", name).decrement *>
+                Metrics.singletons.tagged("singleton_name", name).decrement *>
                 fiber.interrupt.as((name, run, None))
             case other                    => ZIO.succeed(other)
           }

manager/src/main/scala/com/devsisters/shardcake/ShardManager.scala

@@ -76,6 +76,7 @@ class ShardManager(
                              )
                            }
           _             <- ManagerMetrics.pods.decrement
+          _             <- ManagerMetrics.unassignedShards.incrementBy(unassignments.size)
           _             <- eventsHub.publish(ShardingEvent.PodUnregistered(podAddress))
           _             <- eventsHub
                              .publish(ShardingEvent.ShardsUnassigned(podAddress, unassignments))