if ($request_method = 'OPTIONS') {
    add_header 'Access-Control-Allow-Origin' '$http_origin' always;
    add_header 'Access-Control-Allow-Credentials' 'true' always;
    add_header 'Access-Control-Allow-Methods' 'PUT, GET, POST, PATCH, DELETE, OPTIONS' always;
    add_header 'Access-Control-Allow-Headers' 'X-Double-Cookie,Authorization,DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range' always;
    add_header 'Access-Control-Max-Age' 1728000;
    add_header 'Content-Type' 'text/plain charset=UTF-8';
    add_header 'Content-Length' 0;
    add_header "Vary" "Origin";
    return 204;
}

add_header 'Access-Control-Allow-Origin' '$http_origin' always;
add_header 'Access-Control-Allow-Credentials' 'true' always;
add_header 'Access-Control-Allow-Methods' 'PUT, GET, POST, PATCH, DELETE, OPTIONS' always;
add_header 'Access-Control-Allow-Headers' 'X-Double-Cookie,Authorization,DNT,User-Agent,X-Requested-With,If-Modified-Since,Cache-Control,Content-Type,Range' always;
add_header "Vary" "Origin";