fix: use request headers for controller throtlling

[sebastiendan]

Description

This PR adds a throttler guard to get the client IP address from request headers if any, so that throttling works with proxying the faucet with a load balancer.

PR Checklist:

• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added or updated tests that comprehensively prove my change is effective or that my feature works