Allow simple configuration of multi-domain 301 redirect

[Pinolo]

Implementation proposal:

• Add a new template

server {
    listen ${NGINX_DEFAULT_SERVER_PORT};
    server_name ${NGINX_DOMAIN_REDIRECTS};
    return 301 https://${NGINX_DEFAULT_SERVER_NAME}$request_uri;
}

• Add to entrypoint support for the new variable NGINX_DOMAIN_REDIRECTS: if exists, then the template is processed and copied over to the configuration dir
• The variable can contain multiple domain entries, space-separated