calamari 1.4 branch: modify httpd to be reverse proxy instead of WSGI host

[aalba6675]

Since 1.4, the REST API WSGI application is hosted by calamari-lite at localhost:8002. Should httpd should be configured as a reverse proxy instead of wsgi host?

I think USE_X_FORWARDED_HOST = True may be necessary in calamari_web settings.py for rewriting of absolute URLs.

Something like (for all static assets):

    Alias /static /opt/calamari/webapp/content/
    <Location "/static/">
        ProxyPass "!"
        <IfVersion >= 2.4>
            Require all granted
        </IfVersion>
        SetHandler None
    </Location>
    ### repeat for all static assets
    ### proxy to calamari-lite's gevent pywsgi application
   ### Option to disable SSL?
    <Location "/">
        <IfVersion >= 2.4>
            Require all granted
        </IfVersion>
        ProxyPass  "https://localhost:8002/"
        ProxyPassReverse "https://localhost:8002/"
        SetHandler None
    </Location>

For Django: calamari_web/settings.py

USE_X_FORWARDED_HOST = True

If this is correct, I will submit a PR.

[ChristinaMeno]

@aalba6675 We dropped apache as a requirement in 1.4 so there's currently nothing sitting in front of our service. This might be a nice addition to consider as optional config.