Add Rule AddPrefix

[juliens]

Add the ability to add a prefix in the url when the backend is called.

example :

[backends]

[backends.backend-test.servers.server-1]
url = "http:/backend-server"
weight = 1

[frontends]
[frontends.frontend-test]
    backend = "backend-test"
    entryPoints = ["http"]
[frontends.frontend-test.routes.route-host-test]
    rule = "PathPrefix:/test;PathPrefixStrip:/test;AddPrefix:/prefix"

when call http://traefik/test/url => forward http://backend-server/prefix/url

[emilevauge]

@juliens thanks for this one :)
Could you add some documentation in traefik.sample.toml and in docs/ ?

[emilevauge]

LGTM!
Thanks @juliens :)
/cc @containous/traefik

[emilevauge]

Ping @containous/traefik

[Russell-IO]

LGTM 👍

[vdemeester]

LGTM 🐻