MDL-83479 backup: Add hooks to restore process.

- A hook to enable plugins to add extra settings to the restore task.
  This would be placed inside restore_root_task::define_settings()
- A hook to enable plugins to add extra fields to the copy course form. This would be done inside the copy_form class.
- An adjustment to add the restore plan settings to the course restored event data.
  This would be done inside restore_plan::execute().
- A hook to enable extra work inside the asynchronous copy task. To be placed inside asynchronous_copy_task::execute().

lib/classes/task/asynchronous_copy_task.php

@@ -25,8 +25,11 @@
 
 namespace core\task;
 
+use core\di;
 use async_helper;
 use cache_helper;
+use core\hook\manager;
+use core_backup\hook\before_copy_course_execute;
 
 defined('MOODLE_INTERNAL') || die();
 
@@ -125,6 +128,10 @@ class asynchronous_copy_task extends adhoc_task {
         $shortname = $plan->get_setting('course_shortname');
         $shortname->set_value($copyinfo->shortname);
 
+        // Create and dispatch a hook to allow interaction with the task immediately prior to execution.
+        $hook = new before_copy_course_execute($plan, $copyinfo);
+        di::get(manager::class)->dispatch($hook);
+
         // Do some preflight checks on the restore.
         $rc->execute_precheck();
         $status = $rc->get_status();