How i can translate uppercase to lowercase letters in a rewrite rule in nginx web server?

Question

I need to translate the address:

www.example.com/TEST in ---> www.example.com/test

Answer 1

Based on Adam's answer, I ended up using lua, as it's available on my server.

set_by_lua $request_uri_low "return ngx.arg[1]:lower()" $request_uri;
if ($request_uri_low != $request_uri) {
   set $redirect_to_lower 1;
}
if (!-f $request_uri) {
    set $redirect_to_lower "${redirect_to_lower}1";
}
if ($redirect_to_lower = 11) {
    rewrite . https://$host$request_uri_low permanent;
}