Change string to number in API docs for ids
https://community.theforeman.org/t/unable-to-create-or-update-managed-host-via-api/17692 reports that operatingsystem_id should be a nubmer instead of a string in the API documentation. So, the main reason for this issue is to fix this entry.
However, I've noticed that we've got similar inconsistency for ID entries in more than one API doc controller. Those should be probably reviewed to prevent similar issues in the future.