NGINX+ Dynamic Upstream Reloads

[mpstefan]

As a user of NGF using an NGINX+ image
I want NGF to dynamically reload upstreams when the endpoints of the pods of the service of the backend reference changes
So that when I modify my pods in a way that changes their IP address, I do not prompt an NGINX reload.

Acceptance

• When NGF detects that NGINX+ is being used as the data plane, NGF will perform a dynamic reload when the endpoints of the pods of the service of the backend reference changes.
• Content is added to NGF NGINX+ documentation that explains this feature.
• Content is added to the NGF architecture document explaining how NGINX and NGINX+ handle upstream changes.

Dev Notes

• A functional test is likely needed to test all functionality of this story.