# First, add the following to the global config:
lua_package_path '/path/to/ponymail/site/api/?.lua;;';

# Then add this to your server (virtualhost) config:
    root /path/to/ponymail/site;
    location ~ ^/api/([-_a-zA-Z0-9]+)\.lua {
        set $path $1;
        content_by_lua_file /var/www/ponymail/site/api/$path.lua;
    }