Support Keepalived in a Cluster

[riebecj]

Is your feature request related to a problem? Please describe.
No related problem.

Describe the solution you'd like
Have the UI support a keepalived VIP configuration between the nodes. This would require managing the /etc/keepalived/keepalived.conf file, but at a minimum it would require a vrrp_instance on each node, you could use the same node name/secret from the primary node when configuring authentication and pidof nginx-ui and/or systemctl is-active --quiet nginx-ui in the vrrp_script for each node's vrrp_instance. This would allow for a cluster of NginxUI nodes to be HA and fault tolerant.

Describe alternatives you've considered
Manually deploying keepalived to the NginxUI nodes via a separate pipeline.

Additional context
N/A