PUBLIC_SERVER_ADDRESS value can have conflicting requirements

[bferguso]

The PUBLIC_SERVER_ADDRESS is used to

1. generate the URL for export download links, and
2. as a basis for webpack to generate resources.

This can be a problem if:

1. an application is hosted behind a reverse proxy and
2. the externally accessible hostname does not resolve from the server

In this circumstance it appears that only one of the uses of PUBLIC_SERVER_ADDRESS can work for any given value.

For example, our implementation has the following external URL (outside of the reverse proxy, which does not resolve from the server):
https://apps.nrs.gov.bc.ca/bcrhp
but the URL necessary for webpack to generate resources is the hostname:
https://<hostname>:port/bcrhp where the hostname is not accessible to the public.

The external URLs for things like download links can be corrected by overriding default Arches Core views/functions however it seems like the URL used by webpack and for URLs generated for external access should be able to be different.