messages.md

+local/hvp course request is based entirely on core course request.
+There are some adjustments mainly in the request form fields and confirmations.
+
+### How do messages work
+
+Messages use the [Message API](https://docs.moodle.org/dev/Message_API).
+Register as a messageprovider to the message producer. The core messages are registered in
+`/lib/db/messages.php`.   
+
+extract from `/lib/db/messages.php`
+```php
+//...
+// Course creation request notification
+'courserequested' => array (
+    'capability'  => 'moodle/site:approvecourse'
+),
+
+// Course request approval notification
+'courserequestapproved' => array (
+        'capability'  => 'moodle/course:request',
+        'defaults' => array(
+        'airnotifier' => MESSAGE_PERMITTED + MESSAGE_DEFAULT_LOGGEDIN + MESSAGE_DEFAULT_LOGGEDOFF,
+    ),
+),
+
+// Course request rejection notification
+'courserequestrejected' => array (
+    'capability'  => 'moodle/course:request',
+    'defaults' => array(
+        'airnotifier' => MESSAGE_PERMITTED + MESSAGE_DEFAULT_LOGGEDIN + MESSAGE_DEFAULT_LOGGEDOFF,
+    ),
+),
+//  ...
+```
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