feat(UI): Add UI For controlling group join and leave system messages setting

Backported from 069ab92fd0

src/widget/form/settings/generalform.cpp

@@ -144,6 +144,7 @@ GeneralForm::GeneralForm(SettingsWidget* myParent)
     bodyUI->closeToTray->setEnabled(showSystemTray);
 
     bodyUI->statusChanges->setChecked(s.getStatusChangeNotificationEnabled());
+    bodyUI->groupJoinLeaveMessages->setChecked(s.getShowGroupJoinLeaveMessages());
 
     bodyUI->autoAwaySpinBox->setValue(s.getAutoAwayTime());
     bodyUI->autoSaveFilesDir->setText(s.getGlobalAutoAcceptDir());
@@ -215,6 +216,11 @@ void GeneralForm::on_statusChanges_stateChanged()
     Settings::getInstance().setStatusChangeNotificationEnabled(bodyUI->statusChanges->isChecked());
 }
 
+void GeneralForm::on_groupJoinLeaveMessages_stateChanged()
+{
+    Settings::getInstance().setShowGroupJoinLeaveMessages(bodyUI->groupJoinLeaveMessages->isChecked());
+}
+
 void GeneralForm::on_autoAwaySpinBox_editingFinished()
 {
     int minutes = bodyUI->autoAwaySpinBox->value();

src/widget/form/settings/generalform.h

@@ -52,6 +52,7 @@ private slots:
     void on_autoAwaySpinBox_editingFinished();
     void on_minimizeToTray_stateChanged();
     void on_statusChanges_stateChanged();
+    void on_groupJoinLeaveMessages_stateChanged();
     void on_autoacceptFiles_stateChanged();
     void on_maxAutoAcceptSizeMB_editingFinished();
     void on_autoSaveFilesDir_clicked();

src/widget/form/settings/generalsettings.ui

@@ -222,6 +222,13 @@ instead of closing itself.</string>
               </property>
              </widget>
             </item>
+            <item>
+             <widget class="QCheckBox" name="groupJoinLeaveMessages">
+              <property name="text">
+               <string>Add a chat message when a user joins or leaves a group</string>
+              </property>
+             </widget>
+            </item>
            </layout>
           </item>
           <item>
@@ -364,6 +371,7 @@ instead of closing itself.</string>
   <tabstop>minimizeToTray</tabstop>
   <tabstop>closeToTray</tabstop>
   <tabstop>statusChanges</tabstop>
+  <tabstop>groupJoinLeaveMessages</tabstop>
   <tabstop>autoAwaySpinBox</tabstop>
   <tabstop>autoSaveFilesDir</tabstop>
   <tabstop>autoacceptFiles</tabstop>