Employee contract information is being reorganized into dated employee versions so HR teams can see how roles, pay details, and contract data changed over time. This improves payroll accuracy and makes historical employee information easier to manage, while requiring updates across HR-related workflows and localizations.

This will add a versioning system on the employee. Each version is actually the
model hr.contract (that will need to be renamed to version).

Some fields from the employee are moved to hr.contract as they need to be
versioned.

Task: 4564173