REST API metrics by client IP

[steven-sheehy]

Problem
For deployments that we whitelist client IPs, it would be helpful to have REST API metrics broken down by those client IPs so we get more insight into how the clients are using the product.

Solution
Add client's IP to the metric. It might already be there as I see a real_ip listed in some sample elastic output in swagger-stats repo.

Alternatives
Use metrics via a proxy.

Additional Context