The CDN url must be hardcoded at settings.yml:asset_host during assets
compilation in order to get static assets like CSS files point to the
CDN. Otherwise, the assets are generated with relative paths and are
not loaded from the CDN, even when settings.yml:asset_host is set during
runtime. We don't want to have to provide any CDN url when building
porta docker images in order to get the assets correctly precompiled.
To avoid that, this trick assumes the assets are generated with relative
paths (settings.yml:asset_host = null during compilation time) and
prepends the CDN url in runtime.

By default, settings.yml:asset_host is set to RAILS_ASSET_HOST, which
makes this env variable the only source of truth for CDN urls.

Co-authored-by: Aleksandar N. Kostadinov <akostadinov@gmail.com>

We're not going to merge until SaaS is moved to OCP

In order to be able to load both Sprockets and Webpacker assets from a CDN, the asset host property must be empty during the webpack assets compilation time. This ensures urls are generated as relative paths and webpack can safely prepend the CDN url to them.

This reverts commit 2c3e4a8