(#2) - forms improvements (#4)

Co-authored-by: Martin Slachta <martin.slachta@outlook.com>
Reviewed-on: #4

includes/RsvAdminMenuDefinition.php

@@ -4,12 +4,17 @@
  * Contains definitions of the admin menus
  */
 function rsv_admin_menu_definition() {
+    $reservations = new RsvReservationsPage();
+    $forms        = new RsvFormsPage();
+    $timetable    = new RsvTimetablePage();
+    $google_cal   = new RsvGoogleCalendarSettingsPage();
+
     add_menu_page(
         'Reservations Settings',     // Page title
         'Reservations',              // Menu title
         RsvCapabilities::MANAGE,     // Capability
         'reservations-settings',     // Menu slug
-        'rsv_reservations_page', // Callback
+        [$reservations, 'render'],   // Callback
         'dashicons-calendar',        // Icon
         20                           // Position
     );
@@ -20,7 +25,7 @@ function rsv_admin_menu_definition() {
         'Forms',
         RsvCapabilities::MANAGE,
         'forms-settings',
-        'rsv_forms_page'
+        [$forms, 'render']
     );
 
     add_submenu_page(
@@ -29,7 +34,7 @@ function rsv_admin_menu_definition() {
         'Timetables',
         RsvCapabilities::MANAGE,
         'timetable-settings',
-        'rsv_timetable_page'
+        [$timetable, 'render']
     );
 
     add_submenu_page(
@@ -38,6 +43,6 @@ function rsv_admin_menu_definition() {
         'Google Calendar',
         RsvCapabilities::MANAGE,
         'rsv-google-calendar',
-        'rsv_google_calendar_settings_page'
+        [$google_cal, 'render']
     );
 }