remove serverOnly (#496)

As discussed in discord,  removing this flag.
Changing this flag at runtime does not work at all.
and it is also bugged,  see #389

The use case this addresses is to have an object that only lives in the server
but you can easily achieve this by setting an object as active
in the Started and Stopped events in NetworkServer.

In the future, we may reintroduce this if there is a good case for it
with an AOI rewrite

closes #389

BREAKING CHANGE: Remove serverOnly option in NetworkIdentity

Assets/Mirror/Runtime/NetworkIdentity.cs

@@ -113,7 +113,7 @@ public sealed class NetworkIdentity : MonoBehaviour
         /// <summary>
         /// Returns true if running as a client and this object was spawned by a server.
         /// </summary>
-        public bool IsClient => Client != null && Client.Active && NetId != 0 && !serverOnly;
+        public bool IsClient => Client != null && Client.Active && NetId != 0;
 
         /// <summary>
         /// Returns true if NetworkServer.active and server is not stopped.
@@ -157,12 +157,6 @@ public sealed class NetworkIdentity : MonoBehaviour
         [FormerlySerializedAs("m_SceneId"), HideInInspector]
         public ulong sceneId;
 
-        /// <summary>
-        /// Flag to make this object only exist when the game is running as a server (or host).
-        /// </summary>
-        [FormerlySerializedAs("m_ServerOnly")]
-        public bool serverOnly;
-
         /// <summary>
         /// The NetworkServer associated with this NetworkIdentity.
         /// </summary>

Assets/Mirror/Runtime/ServerObjectManager.cs

@@ -424,9 +424,6 @@ internal void SpawnObject(GameObject obj, INetworkConnection ownerConnection)
 
         internal void SendSpawnMessage(NetworkIdentity identity, INetworkConnection conn)
         {
-            if (identity.serverOnly)
-                return;
-
             // for easier debugging
             if (logger.LogEnabled()) logger.Log("Server SendSpawnMessage: name=" + identity.name + " sceneId=" + identity.sceneId.ToString("X") + " netid=" + identity.NetId);