fixes #28655 - support fetching files via /pulp/isos with pulp3

[wbclark]

This is a WIP. Currently it should disable isos for pulp2 when $enable_pulpcore_file but it does not yet add the vhost entry for proxying /pulp/isos to the pulpcore content app

[wbclark]

Looking for feedback on the right place to set $enable_pulpcore_file to true -- whether that should just be default here or explicitly called in another repo.

[ehelms]

The default should be true going forward, in a Katello upgrade scenario we will need this value t be false. However, that will be confusing to users of this module potentially. As we need to support:

• Pulp 2 and Pulp 3 running with File support
• Apache configured to proxy /pulp/isos to Pulp 3 content app instead of sending /pulp/isos to Pulp 2

I think the second bullet will need a specific parameter to do what your code is doing here and add an entry to the vhost for proxying

[wbclark]

Thanks @ehelms . I think the second bullet should be adequately addressed by theforeman/puppet-pulpcore#55 which should also be enabled once $enable_pulpcore_file is set to true here.

About the first bullet point, I think it's adequately solved as well if I understand correctly the existing $enable_iso and $enable_file params. The new $enable_pulpcore_file won't affect the existing $enable_file but it will override $enable_iso to be always false. So IIUC, this leaves the possibility for the pulp2 file module to be enabled but not ISOs specifically. Please let me know if I got that correct.

[wbclark]

The latest iteration changes the name of the new parameter to $proxy_pulp_isos_to_pulpcore to make it clear that this isn't responsible for whether the file plugin is enabled in pulpcore.

Additionally, the actual ProxyPass logic is moved into this module since the /pulp/isos path is a Katello-ism that doesn't exist in standalone pulp{,core}

[wbclark]

Added tests and I believe those should be working as expected after the latest push.