Move ExternalName to OSS

[AlexFenlon]

resolver directive is now in NGINX OSS due to this, ExternalName can be migrated to be OSS instead of Plus Exclusive

Example: https://github.com/nginx/kubernetes-ingress/blob/main/examples/ingress-resources/externalname-services/README.md

• make resolver ConfigMap key available in NGINX OSS

[github-actions]

Hi @AlexFenlon thanks for reporting!

Be sure to check out the docs and the Contributing Guidelines while you wait for a human to take a look at this 🙂

If your issue concerns any of the enterprise features please open a ticket with F5 directly (For NGINX Plus customers NGINX Ingress Controller (when used with NGINX Plus) is covered by the support contract.)

Cheers!