[plugin] Allow usage of the X-Forwarded-For header in the ip-restriction plugin

[Tieske]

When behind a proxy the ip-restriction plugin will act upon the ip address of the proxy, instead of the original client, passed in the X-Forwarded-For header.

Requires an option to be added to the schema to (dis)allow this.

[jammm]

It would be useful if this can be done for the rate limiting plugin as well, in case it falls back to IP as the identifier for rate limiting.

[subnetmarco]

@Tieske I have tried to replicate, unsuccessfully. Can you take a look at the test? #2019

We are using the ngx_http_realip_module module under the hood to transparently handle this.

[bungle]

I'm pretty sure this is handled with #2236 / #2202.

[bungle]

@Tieske is this relevant anymore as the we have merged the above?

[Tieske]

let's close this.