Add API endpoint for Appraisals, One to Ones and Probation

We would love to be able to extract Appraisal, One to One and Probation data so we can set up reporting to alert when these are overdue. This reporting would be great to have for our business as we rely a lot on these metrics and the process for extracting the data is currently very manual. It would be great to add this data to the automation we already have set up for absences and holidays.