SimpleStreams official documentation miss structure and references

Ubuntu Version:
Ubuntu noble 24.04 LTS

Problem Description:
We’re currently trying to gain more in depth knowledge about the simple streams product as part of our maas deployment.

I’ve found and read the “official” simple streams documentation in here: Simple streams documentation.

But, I’m looking for a more advanced documentation about which structure does it wait for/create and various other details such as:

  • Is the simple streams structure requiring signed index or are those signed index optionals?
  • Is there a specific directory tree arborescence expected?

The official documentation doesn’t seems to be very explicit about such details although there are some index json schema and product json schema, it doesn’t specify if signed artifacts are required or how the content directories must be structured (or if defined at all).

Is there any additional documentation that I would have missed somewhere and that indeed describe the internals of simple streams?

Our goal is to be able to setup a fully offline deployment of maas as well as the ability to provide custom provisioning images on it to be able to manage our specific (currently unsupported) HW.

The custom images management feature is the last part of it.