Bug: ponymail_httpd_docker.conf wrong lua version and paths?

ponymail_httpd_docker.conf contains:

```
LuaPackageCPath /usr/lib/lua/5.3/?.so
LuaPackagePath /usr/share/lua/5.3/?.lua
```

However AFAICT apache2/httpd currently only supports Lua 5.2

Also, when I build the Docker image, there is no path /usr/lib/lua; instead there is /usr/lib/x86_64-linux-gnu/lua

Start with ponymail_httpd_docker.conf and inspect how the Docker image provides Lua and Apache httpd support. Verify whether the configured Lua 5.3 paths match the supported version and the image's actual library locations. Done means the configuration uses the correct version and paths for the built image.

Written by the indexing model from the issue text.