Add support for K8S Ingress Header X-Original-Forwarded-For

[Ismaaa]

Hey there! I've added support for the X-Original-Forwarded-For header, which is used by Kubernetes Ingress.

I've also put together a few tests to make sure everything works as expected:

• One test checks if we correctly pick the first IP when a list is passed.
• Another test makes sure we handle an 'unknown' IP gracefully and pick the next valid one.
• The last test ensures we correctly extract the IP when it comes with a port.

I believe these changes will make IP resolution in Kubernetes Ingress environments even better. Please have a look and let me know what you think.

[patunalu]

Is this library sill maintained?

[spathon]

Nice, but shouldn't it be before x-forwarded-for?