Provide config/server.yaml at runtime via Helm

[bodom0015]

Feedback from @manning-ncsa on preliminary prototype:

It looks like many of flexibilities have been removed from the job manager, making this more complicated than it should be. For example, the server config was removed as a mounted ConfigMap and I guess is now hard-coded from the Docker build? If this were set from a ConfigMap, then it would be easy to tune the resource requests/limits and/or change the job image:tag via the ArgoCD web UI without rebuilding/pushing a new job-manager image.

This seems like a great idea! We can change the Helm chart to mount this file into the deployment

The source code can contain a server.yaml with values that work for local development, and our production config can override this file at runtime to change the hostnames, ports, resource limits, etc

[bodom0015]

Partially completed by #22, which allows us to override some necessary parts of the server.yaml file at runtime

The logic is currently a bit too-specific to the format of this YAML file, so we might as well just mount the entire server.yaml as a file from configmap. I believe SPT-3G mounts the entire file from a configmap as well