feat(chatlog): Disable join and leave system messages based on setting

Backported from 069ab92fd0

src/widget/form/groupchatform.cpp

@@ -235,13 +235,17 @@ void GroupChatForm::updateUserNames()
 
 void GroupChatForm::onUserJoined(const ToxPk& user, const QString& name)
 {
-    addSystemInfoMessage(tr("%1 has joined the group").arg(name), ChatMessage::INFO, QDateTime::currentDateTime());
+    if (settings.getShowGroupJoinLeaveMessages()) {
+        addSystemInfoMessage(tr("%1 has joined the group").arg(name), ChatMessage::INFO, QDateTime::currentDateTime());
+    }
     updateUserNames();
 }
 
 void GroupChatForm::onUserLeft(const ToxPk& user, const QString& name)
 {
-    addSystemInfoMessage(tr("%1 has left the group").arg(name), ChatMessage::INFO, QDateTime::currentDateTime());
+    if (settings.getShowGroupJoinLeaveMessages()) {
+        addSystemInfoMessage(tr("%1 has left the group").arg(name), ChatMessage::INFO, QDateTime::currentDateTime());
+    }
     updateUserNames();
 }