nginx.conf

# target server
upstream postgrest {
        server localhost:4000;
        keepalive 64;
}

# proxy
server {
        listen 3000;
  
        # forward /api/* to postgrest
        location /api/ {
                proxy_pass http://postgrest/;
        }
        
        # forward /urlauth/<TOKEN>/* to postgrest and set Authorization-header from URL
        location ~ ^/urlauth/(.*)/(.*)$ {
                proxy_set_header Authorization "Bearer $1";
                proxy_pass http://postgrest/$2$is_args$args;
        }
}