window: Add "Online Accounts..." button

data/ui/window.ui

@@ -301,6 +301,15 @@
         <property name="margin">12</property>
         <property name="orientation">vertical</property>
 
+        <!-- About -->
+        <child>
+          <object class="GtkModelButton">
+            <property name="visible">True</property>
+            <property name="action-name">win.open-online-accounts</property>
+            <property name="text" translatable="yes">_Online Accounts…</property>
+          </object>
+        </child>
+
         <!-- Weather -->
         <child>
           <object class="GtkModelButton">

src/gui/gcal-window.c

@@ -391,6 +391,16 @@ on_window_new_event_cb (GSimpleAction *action,
   gtk_widget_show (self->edit_dialog);
 }
 
+static void
+on_window_open_online_accounts_cb (GSimpleAction *action,
+                                   GVariant      *param,
+                                   gpointer       user_data)
+{
+  GApplication *application = g_application_get_default ();
+
+  gcal_utils_launch_online_accounts_panel (g_application_get_dbus_connection (application), NULL, NULL);
+}
+
 static void
 on_window_previous_date_activated_cb (GSimpleAction *action,
                                       GVariant      *param,
@@ -1084,6 +1094,7 @@ gcal_window_init (GcalWindow *self)
     {"change-view", on_view_action_activated, "i" },
     {"next-date", on_window_next_date_activated_cb },
     {"new-event", on_window_new_event_cb },
+    {"open-online-accounts", on_window_open_online_accounts_cb },
     {"previous-date", on_window_previous_date_activated_cb },
     {"show-calendars", on_show_calendars_action_activated },
     {"today", on_window_today_activated_cb }