Traefik: Add more granular APIs to manage Traefik's configuration

[007reader]

Do you want to request a feature or report a bug?

feature

What I'd like to see?

I use API to manage Traefik configuration (https://docs.traefik.io/configuration/api/). It allows to update provider's configuration via PUT /api/providers/{provider} API call. In some cases the payload can become pretty large, although the actual changes can be really small, e.g. one additional routing rule.

It would be great to enable PUT on every endpoint to allow to manage at a more granular level. E.g. currently, there is an API /api/providers/{provider}/backends/{backend} to get backend config, but it only supports GET method. Having PUT method would enable user to manage individual backend without reading the entire configuration.

In ideal, I'd love to see PUT method on every API starting with /api/providers/{provider} and below

[timoreimann]

It might be good to think about PATCH support as well so that delta changes may be submitted.