redirect all http queries to https and allow Let's encrypt challenge.

000-default-80.conf

#
# HTTP: Let's encrypt + redirect on HTTPs
#
<VirtualHost _default_:80>
    ServerAdmin [email protected]

    ### Let's encrypt
    Alias /.well-known/acme-challenge/ /var/www/challenges/
    <Directory "/var/www/challenges">
        # Allow open access:
        Require all granted
    </Directory>

    ### Redirect to HTTPs
    RewriteEngine on
    RewriteCond %{REQUEST_URI} !^/.well-known/acme-challenge/
    RewriteRule (.*) https://%{HTTP_HOST}$1 [R=301,L]
</VirtualHost>