Add support for Nexus Docker Subdomain Connector

I would like to request that Support for the Nexus Docker Subdomain Connector be added to the chart. This would result in the additional capability to dynamically create Istio Virtual services that have defined subdomain hosts that point to the nexus-repository-manager service.

This negates the need to have to open up ports and modify the PPSM for each docker registry added. This change would also still allow the current docker registry port pattern.

I have created a feature branch (https://repo1.dso.mil/big-bang/product/packages/nexus/-/tree/nexus-docker-subdomain-enable) off of the main branch and tested this works successfully:

I am not sure of the process for an MR as this is my first contribution as a developer to a BB Addon Chart. Please advise.

Reference Links:

https://help.sonatype.com/repomanager3/nexus-repository-administration/formats/docker-registry/docker-subdomain-connector https://blog.sonatype.com/scale-up-your-enterprise-with-docker-subdomain-routing