Refactor sync and locallib classes

The classes/sync.php file is quite long and hard to get an overview what is happening. I propose splitting it up into smaller pieces. The classes/locallib.php contains all sort of statics functions, I was wondering a lot, whether they could be grouped better, but I am just getting started with the plugins structure.

Ideas:

Seperate CAMPUSonline-API functions and Moodle mappings/features (maybe use traits).
Link the CAMPUSonline API in the PHPdocs where it gets called.
Make us of Enums for constants like GROUP_TO_COURSE.
...

The refactoring should take future seperation of plugins into account as described in #74

Edited Jun 18, 2025 by André Menrath

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