Currently, when developing custom policies, there is no easy way to include or use external Lua libraries.
The request is to provide a way to easily add Lua dependencies to APIcast. This will enable a lot more flexibility for users building custom policies as it will allow making use of external dependencies not included in the productized image.
: https://github.com/3scale-demos/apicast-json-to-xml (small policy that transforms JSON response to XML. It explains how to use external dependencies.)