MDL-77350 rating: Added class properties that are not declared

In PHP 8.2 and later, setting a value to an undeclared class property is
deprecated and emits a deprecation notice.
So we need to add missing class properties that still need to be declared.

rating/tests/externallib_test.php

@@ -46,6 +46,45 @@ require_once($CFG->dirroot . '/rating/lib.php');
  */
 class externallib_test extends externallib_advanced_testcase {
 
+    /** @var \stdClass course record. */
+    protected $course;
+
+    /** @var \stdClass user record. */
+    protected $student1;
+
+    /** @var \stdClass user record. */
+    protected $teacher1;
+
+    /** @var \stdClass user record. */
+    protected $student2;
+
+    /** @var \stdClass user record. */
+    protected $teacher2;
+
+    /** @var \stdClass user record. */
+    protected $student3;
+
+    /** @var \stdClass user record. */
+    protected $teacher3;
+
+    /** @var \stdClass activity record. */
+    protected $forum;
+
+    /** @var \stdClass activity record. */
+    protected $discussion;
+
+    /** @var int context instance ID. */
+    protected $contextid;
+
+    /** @var \stdClass forum post. */
+    protected $post;
+
+    /** @var \stdClass a fieldset object, false or exception if error not found. */
+    protected $studentrole;
+
+    /** @var \stdClass a fieldset object, false or exception if error not found. */
+    protected $teacherrole;
+
     /*
      * Set up for every test
      */