Optimize default nginx config

[sjberman]

Problem: We want to ensure that the default nginx configuration uses the best possible options for performance and stability.

Solution: Using NGINX Ingress Controller as a guide, added options to increase performance, set the common X-Forwarded-For header, and allow standard media types.

Closes #557

• I have read the CONTRIBUTING doc
• I have added tests that prove my fix is effective or that my feature works
• I have checked that all unit tests pass after adding my changes
• I have updated necessary documentation
• I have rebased my branch onto main
• I will ensure my PR is targeting the main branch and pulling from my branch from my own fork

[kate-osborn]

Part of the AC for #1040 is to review the config with NGINX experts. Has that been done? Should we tag an expert on this PR?

[sjberman]

Part of the AC for #1040 is to review the config with NGINX experts. Has that been done? Should we tag an expert on this PR?

I haven't done that specifically. These changes were based on NIC's default configuration, module docs, multiple online guides for optimizing NGINX, and a default configuration as provided by nginx docs (using what is relevant to NKG). All of those resources influenced these minimal changes. There really aren't that many options for us to work with for a default configuration, so I felt that asking someone specifically may be overkill (and overhead) that wouldn't offer much more value that the research hasn't already offered.