Add documentation on serving Datasette behind a proxy using base_url

[simonw]

This can go on this page: https://docs.datasette.io/en/stable/deploying.html

Refs #1023, #865

[simonw]

It should cover both nginx and Apache. nginx config is here: #1024 (comment)

[simonw]

I'll install Apache on macOS to figure this out using https://formulae.brew.sh/formula/httpd

brew install httpd output this at the end:

==> httpd
DocumentRoot is /usr/local/var/www.

The default ports have been set in /usr/local/etc/httpd/httpd.conf to 8080 and in
/usr/local/etc/httpd/extra/httpd-ssl.conf to 8443 so that httpd can run without sudo.

To have launchd start httpd now and restart at login:
  brew services start httpd
Or, if you don't want/need a background service you can just run:
  apachectl start

[simonw]

Running apachectl -X appears to run Apache in the foreground so I can hit Ctrl+C to quit it again, using the config file at /usr/local/etc/httpd/httpd.conf and serving the index.html file from /usr/local/var/www (which confusingly says "Welcome to nginx", presumably because I installed nginx via Homebrew earlier).

[simonw]

Still need to configure proxying though. https://www.netnea.com/cms/apache-tutorial-9_setting-up-a-reverse-proxy/

[simonw]

On my Mac, I run:

datasette . -p 8009 --config base_url:/datasette-prefix/

Then I edited /usr/local/etc/httpd/httpd.conf and add this section:

LoadModule proxy_module lib/httpd/modules/mod_proxy.so
LoadModule proxy_http_module lib/httpd/modules/mod_proxy_http.so
ProxyPass          /datasette-prefix/    http://localhost:8009/datasette-prefix/

I ran Apache in the foreground like so:

apachectl -X

Now hitting http://localhost:8081/datasette-prefix/fixtures/compound_three_primary_keys worked!