Fix a nostr subscription registration bug (#201)

* check the dictionary _eoseCalledOnSubscriptionClients before adding a subscription class

* log if the subscription is already monitored

* return the result of the method adding the subscription

* log at the caller

src/Angor/Shared/Services/INostrCommunicationFactory.cs

@@ -8,7 +8,7 @@ public interface INostrCommunicationFactory
     void CloseClientConnection();
     int GetNumberOfRelaysConnected();
     bool EoseEventReceivedOnAllRelays(string subscription);
-    void MonitoringEoseReceivedOnSubscription(string subscription);
+    bool MonitoringEoseReceivedOnSubscription(string subscription);
     void ClearEoseReceivedOnSubscriptionMonitoring(string subscription);
     bool OkEventReceivedOnAllRelays(string eventId);
     void MonitoringOkReceivedOnSubscription(string eventId);

src/Angor/Shared/Services/NostrCommunicationFactory.cs

@@ -114,10 +114,10 @@ public bool EoseEventReceivedOnAllRelays(string subscription)
         return response;
     }
 
-    public void MonitoringEoseReceivedOnSubscription(string subscription)
+    public bool MonitoringEoseReceivedOnSubscription(string subscription)
     {
         _logger.LogInformation($"Started monitoring subscription {subscription}");
-        _eoseCalledOnSubscriptionClients.Add(subscription, new List<string>());
+        return _eoseCalledOnSubscriptionClients.TryAdd(subscription, new List<string>());
     }
 
     public void ClearEoseReceivedOnSubscriptionMonitoring(string subscription)

src/Angor/Shared/Services/RelaySubscriptionsHandling.cs

@@ -1,4 +1,5 @@
 using System.ComponentModel;
+using Blockcore.EventBus;
 using Microsoft.Extensions.Logging;
 using Nostr.Client.Requests;
 using Nostr.Client.Responses;
@@ -65,9 +66,12 @@ public void HandleOkMessages(NostrOkResponse okResponse)
 
     public bool TryAddEoseAction(string subscriptionName, Action action)
     {
-        _communicationFactory.MonitoringEoseReceivedOnSubscription(subscriptionName);
-
-        return userEoseActions.TryAdd(subscriptionName,action);
+        var add = _communicationFactory.MonitoringEoseReceivedOnSubscription(subscriptionName);
+
+        if (!add)
+            _logger.LogWarning($"Subscription {subscriptionName} is already being monitored");
+
+        return userEoseActions.TryAdd(subscriptionName,action); 
     }
 
     public void HandleEoseMessages(NostrEoseResponse _)