- An employee isn't required anymore on a contract, to allow default contract for a certain job
- Remove trial_date_start, as we assume that it's the same than the contract date start
- wage should be a fields.Monetary
- Add a state 'cancel' for a contract
- Move some fields to the employee (permit number, visa number, visa expiration date)
- Add company and currency on the contract
- Restructure contract form view in a so beautiful way