Publish ApplicationStartingEvent during startup

Fixes #3102

(cherry picked from commit 5400bce1295bdc4198d2cfe0b9258bbb7ccf0852)

src/NzbDrone.Host/Startup.cs

@@ -25,6 +25,9 @@ using NzbDrone.Common.Serializer;
 using NzbDrone.Core.Configuration;
 using NzbDrone.Core.Datastore;
 using NzbDrone.Core.Instrumentation;
+using NzbDrone.Core.Lifecycle;
+using NzbDrone.Core.Messaging.Events;
+using NzbDrone.Host;
 using NzbDrone.Host.AccessControl;
 using NzbDrone.Http.Authentication;
 using NzbDrone.SignalR;
@@ -215,7 +218,8 @@ namespace NzbDrone.Host
                               IConfigFileProvider configFileProvider,
                               IRuntimeInfo runtimeInfo,
                               IFirewallAdapter firewallAdapter,
-                              LidarrErrorPipeline errorHandler)
+                              LidarrErrorPipeline errorHandler,
+                              IEventAggregator eventAggregator)
         {
             initializeLogger.Initialize();
             appFolderFactory.Register();
@@ -236,6 +240,8 @@ namespace NzbDrone.Host
                 Console.CancelKeyPress += (sender, eventArgs) => NLog.LogManager.Configuration = null;
             }
 
+            eventAggregator.PublishEvent(new ApplicationStartingEvent());
+
             if (OsInfo.IsWindows && runtimeInfo.IsAdmin)
             {
                 firewallAdapter.MakeAccessible();