Trying to get a header from an auth_request into a variable and use it from Lua with no luck. This was the simple example I tried.

location = /auth {
add_header X-Boo "Hello World";
return 204;
}

location /test {
auth_request /auth;
auth_request_set $test $upstream_http_x_boo;
add_header X-BooHoo $test;

content_by_lua '
ngx.say("(" .. ngx.var.test .. ")")
';
}