ignore UTM parameters from varnish hashing function

hash.vcl

sub vcl_hash {
    # Strip out Google Analytics campaign variables
    # They are only needed by the javascript running on the page
    # utm_source, utm_medium, utm_campaign, gclid, …

    hash_data(regsub(regsuball(req.url, "(vid|ef_id|gclid|kw|cof|siteurl|zanpid|origin|emst|sc_[a-z]+|utm_[a-z]+|mr:[A-z]+)=[%@\.\-\:\+_A-z0–9]+&?", ""), "(\?&|\?|&)$", ""));

    if (req.http.X-Forwarded-Proto ~ "^(https|http)$") {
        hash_data(req.http.X-Forwarded-Proto);
    }

    if (req.http.host) {
        hash_data(req.http.host);
    } else {
        hash_data(server.ip);
    }
    return (lookup);
}