Refactor dependencies to reduce code base size (#111)

Use crates to reduce code base size :

* `actix-remote-ip` to safely determine user IP location
* `light-openid` for the OpenID primitives & as client to handle federation

Reviewed-on: #111

templates/settings/account_details.html

@@ -30,4 +30,6 @@
     </tbody>
 </table>
 
+<p>Your IP address: {{ remote_ip }}</p>
+
 {% endblock content %}