Adds function to parse VersionedModuleSchema from base64

[soerenbf]

Purpose

Needed this for the custom indexer epic, thought it could be useful elsewhere as well.

Changes

• Add from_base64_str to VersionedModuleSchema

Checklist

• [x] My code follows the style of this project.
• [x] The code compiles without warnings.
• [x] I have performed a self-review of the changes.
• [x] I have documented my code, in particular the intent of the hard-to-understand areas.
• [x] (If necessary) I have updated the CHANGELOG.