Description
Create a global option to allow configuration of the trailing_slash_on_root option at route level.

As I am building an api, I never need the trailing slash and I have to mention the option on a lot of place with the false value. As for me false should be the default value and I don't remember if I need to configure at the leaf route level or if I can define at the parent level (root level seems to not work), I would like to have a framework.router.trailing_slash_on_root configuration (name has to be defined) could be an improvement on this.

The option appears 53 times in my code, always with false value.

Example

# a-lot-of-my-routes-configuration-files.yaml
api_route_resource:
  resource: ./route-resource.yaml
  prefix: /route
  name_prefix: routes_
  trailing_slash_on_root: false

# Possible new config/packages/routing.yaml content
framework:
    router:
        trailing_slash_on_root: false

# new-a-lot-of-my-routes-configuration-files.yaml
api_route_resource:
  resource: ./route-resource.yaml
  prefix: /route
  name_prefix: routes_

I hope this idea can help some people and I am not the only one concerned. Also I hope to not have missed something in the documentation. ;-)

Thank you.