feat: add loa requests

This commit adds a feature that allows users to request periods of inactivity from their managers. This is effectively known as a leave of absence.

The commit also introduces new permissions and migrations, therefore, you'll need to adapt your database according to these changes.

app/Exceptions/AbsenceNotActionableException.php

@@ -0,0 +1,10 @@
+<?php
+
+namespace App\Exceptions;
+
+use Exception;
+
+class AbsenceNotActionableException extends Exception
+{
+    //
+}