Apply introduction changes to existing employees

Turning off new employee introductions only changes who gets asked from now on. Employees who were invited while the setting was on still see the introduction prompt.

What we'll add:

• The setting still controls whether people invited from now on are asked to introduce themselves. Turning it on does not ask people who are already in the organisation.

• Turning it off asks whether that applies to new employees only, or also to existing employees who have not introduced themselves yet.

• Choosing existing employees clears the prompt for those who have not posted an introduction. People who already introduced themselves stay as they are.