New: ical is available with API key authentication

src/NzbDrone.Api/Authentication/EnableStatelessAuthInNancy.cs

@@ -29,7 +29,7 @@ namespace NzbDrone.Api.Authentication
 
             var apiKey = GetApiKey(context);
 
-            if (context.Request.IsApiRequest() && !ValidApiKey(apiKey))
+            if ((context.Request.IsApiRequest() || context.Request.IsFeedRequest()) && !ValidApiKey(apiKey))
             {
                 response = new Response { StatusCode = HttpStatusCode.Unauthorized };
             }

src/NzbDrone.Api/Extensions/RequestExtensions.cs

@@ -10,6 +10,11 @@ namespace NzbDrone.Api.Extensions
             return request.Path.StartsWith("/api/", StringComparison.InvariantCultureIgnoreCase);
         }
 
+        public static bool IsFeedRequest(this Request request)
+        {
+            return request.Path.StartsWith("/feed/", StringComparison.InvariantCultureIgnoreCase);
+        }
+
         public static bool IsSignalRRequest(this Request request)
         {
             return request.Path.StartsWith("/signalr/", StringComparison.InvariantCultureIgnoreCase);