Add a configuration form

Problem/Motivation

Urls and IPs have to be write in a configuration form.

Steps to reproduce

See the file src/Routing/RouteSubscriber.php.
For now only route user.login is checked and not configurable and IPs are to be set in the settings.php file like this :

$config['restrict_admin']['ip'] = [
 '127.0.0.1'
];

Proposed resolution

• Create a configuration form in the admin interface to configure routes to be restrict.
• For each route, a list of IPs (or range of IPs) have to be configure.
• Give the possibility to disable the restricted access for each route
• Set a different configuration for each route to simplify the activation/desactivation on different environments (use configuration entities)