Notification: Fix incorrectly dropped recovery & ACK notifications

Previously, recovery and ACK notifications were not delivered to users
who weren't notified about the problem state while having a configured
`Problem` type filter. However, since the type filter can also be
configured on the `Notification` object level, this resulted to an
incorrect behaviour. This PR changes the existing logic so that the
recovery and ACK notifications gets dropped only if the `Problem` filter
is configured on both the `User` and `Notification` object levels.

lib/icinga/notification.cpp

@@ -428,9 +428,14 @@ void Notification::BeginExecuteNotification(NotificationType type, const CheckRe
 			continue;
 		}
 
+		// Verify if the 'Problem' filter is configured at both the User and Notification object levels.
+		bool foundProblemFilter = NotificationProblem & user->GetTypeFilter() & GetTypeFilter();
+
 		/* on recovery, check if user was notified before */
 		if (type == NotificationRecovery) {
-			if (!notifiedProblemUsers->Contains(userName) && (NotificationProblem & user->GetTypeFilter())) {
+			// Do not send a recovery notification to the current user if he was not previously notified of the
+			// problem state, while containing the 'Problem' filter at both the user and notification object levels.
+			if (!notifiedProblemUsers->Contains(userName) && foundProblemFilter) {
 				Log(LogNotice, "Notification")
 					<< "Notification object '" << notificationName << "': We did not notify user '" << userName
 					<< "' (Problem types enabled) for a problem before. Not sending Recovery notification.";
@@ -440,7 +445,9 @@ void Notification::BeginExecuteNotification(NotificationType type, const CheckRe
 
 		/* on acknowledgement, check if user was notified before */
 		if (type == NotificationAcknowledgement) {
-			if (!notifiedProblemUsers->Contains(userName) && (NotificationProblem & user->GetTypeFilter())) {
+			// Do not send an ACK notification to the current user if he wasn't previously notified of the problem
+			// state, while containing the 'Problem' filter at both the user and notification object levels.
+			if (!notifiedProblemUsers->Contains(userName) && foundProblemFilter) {
 				Log(LogNotice, "Notification")
 					<< "Notification object '" << notificationName << "': We did not notify user '" << userName
 					<< "' (Problem types enabled) for a problem before. Not sending acknowledgement notification.";