feat: add ntfy as notification method (#377)

migrations/000021.php

@@ -0,0 +1,15 @@
+<?php
+
+/* 
+* This migration adds tables to store the data about a new notification method Ntfy
+*/
+
+/** @noinspection PhpUndefinedVariableInspection */
+$db->exec('CREATE TABLE IF NOT EXISTS ntfy_notifications (
+    enabled BOOLEAN DEFAULT 0,
+    host TEXT DEFAULT "",
+    topic TEXT DEFAULT "",
+    headers TEXT DEFAULT "",
+    user_id INTEGER,
+    FOREIGN KEY (user_id) REFERENCES user(id)
+)');