Draft: Fix function types and defaults

What does this merge request do and why?

We need to follow a strict type system in order to keep our code readable. We have to be extra mindful of types in python because there are no compilers to catch type errors for us.

This MR fixes some type errors around GitLabCodeCreationModelHandle, because it needs another function signature other then the one defined in the interface (ModelHandle)

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

Merge request checklist

• I've ran the affected pipeline(s) to validate that nothing is broken.
• Tests added for new functionality. If not, please raise an issue to follow up.
• Documentation added/updated, if needed.