Refactor core for better readability

**Feature request**
It would be great to have logging for models.

**Use case**
Many users need this functionality for production deployments.

**Implementation idea**
Add a new config option `enable_logging` with default `false`.

The issue names no files, tests, or entry points. Start by locating configuration handling and model execution in the repository, then determine which model events need logging and how the enable_logging default should behave; done means the option is documented, disabled by default, and logging works when enabled.

Written by the indexing model from the issue text.