Essentially this moves them to using the API server URL in order for cookies to
work properly when writing.

I originally intended to use the main site URL and have cloudfront route
requests to the backend. This works, except that we're using cookie based
sessions which then don't match the URL being used, so essentially all calls to
the backend have to use the Datomic ions url. This works out fine, since these
URLs should never be displayed to users anyway (though they're not secrets so if
they find them it's fine).