Implement comments (#10)

Allow logged users to comment posts. Edition is not allowed via the API since it doesn't support auth yet.

Symfony UX is used with Turbo to avoid full pages reload, without JavaScript™.

Co-authored-by: clfreville2 <clement.freville2@etu.uca.fr>
Reviewed-on: https://codefirst.iut.uca.fr/git/clement.freville2/herbarium/pulls/10

templates/post/_form.html.twig

@@ -1,4 +1,4 @@
 {{ form_start(form) }}
     {{ form_widget(form) }}
-    <button class="btn">{{ button_label|default('Save') }}</button>
+    <button class="btn btn-primary">{{ button_label|default('Save') }}</button>
 {{ form_end(form) }}