(#2) - forms improvements (#4)

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

includes/RsvAdminPage.php

@@ -0,0 +1,15 @@
+<?php
+
+abstract class RsvAdminPage {
+
+    final public function render(): void {
+        if (!current_user_can(RsvCapabilities::MANAGE)) {
+            return;
+        }
+        echo '<div class="wrap">';
+        $this->render_content();
+        echo '</div>';
+    }
+
+    abstract protected function render_content(): void;
+}