aws-load-balancer-controller: Certificate with extra issuerRef conf

[siryur]

Issue

#1242

Description of changes

[aws-load-balancer-controller]
Add an extra block to the Certificate generated once
enableCertManager: true to allow to set the issuer (ref) group

Checklist

• Added/modified documentation as required (such as the README.md for modified charts)
• Incremented the chart version in Chart.yaml for the modified chart(s)
• Manually tested. Describe what testing was done in the testing section below
• Make sure the title of the PR is a good description that can go into the release notes

Testing

The group is available, if the values contain:

enableCertManager: false

Results in: No change

---

enableCertManager: true
certManager:
  extraIssuerRef:

Results in:

# ...
  issuerRef:
    kind: Issuer
    name: aws-load-balancer-selfsigned-issuer
# ...

---

enableCertManager: true
certManager:
  extraIssuerRef:
    group: cert-manager.io

Results in:

# ...
  issuerRef:
    kind: Issuer
    name: aws-load-balancer-selfsigned-issuer
    group: cert-manager.io
# ...

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.