feat: adds flash message

app/templates/message.html

@@ -0,0 +1,7 @@
+{% with messages = get_flashed_messages() %}
+{% if messages %}
+  <div class="alert alert-{{messages[0].alertType}} mb-4" role="alert">
+      <p class="mb-0">{{ messages[0].message }}</p>
+  </div>
+{% endif %}
+{% endwith %}