Allow deployment with manually installed TLS Secrets

[AndrewEckart]

This PR modifies the chart to allow cluster admins to deploy ServiceX with TLS-enabled Ingress by manually installing TLS Secrets containing certificates onto their cluster. This is an alternative to using cert-manager, and makes it optional where it was previously required.

Changes to the chart are as follows:

• TLS-related values are organized under app.ingress.tls
• To enabled TLS, you must set app.ingress.tls.enabled to true.
• If using cert-manager, the only other thing you have to do is set app.ingress.tls.clusterIssuer (this is now empty by default).
• If installing the secrets manually, you must install the certs.
  By default, the Ingress will look for a Secret named <helm release name>-app-tls, but you can change this by setting app.ingress.tls.secretName.
• Repeat for Minio.

A full config without cert-manager would look something like:

app:
  ingress:
    enabled: true
    host: servicex.ssl-hep.org
    tls:
      enabled: true
      secretName: my-release-app-tls  # optional
minio:
  ingress:
    enabled: true
    annotations:
      kubernetes.io/ingress.class: nginx
    hosts:
    - my-release-minio.servicex.ssl-hep.org
    tls:
    - hosts:
      - my-release-minio.servicex.ssl-hep.org
      secretName: my-release-minio-tls

A full config with cert-manager would look like:

app:
  ingress:
    tls:
      enabled: true
      clusterIssuer: letsencrypt-prod
minio:
  ingress:
    enabled: true
    annotations:
      kubernetes.io/ingress.class: nginx
      cert-manager.io/cluster-issuer: letsencrypt-prod
      acme.cert-manager.io/http01-edit-in-place: "true"
    hosts:
    - my-release-minio.servicex.ssl-hep.org
    tls:
    - hosts:
      - my-release-minio.servicex.ssl-hep.org
      secretName: my-release-minio-tls

Partially addresses #222.

[BenGalewsky]

Great - like the complete documentation with this and the removal of ATLAS bias!