Check user has privileges for service point

When an item is checked out
Then the user performing the check out should have privileges to perform actions at the check out service point

When an item is checked in
Then the user performing the check in should have privileges to perform actions at the check in service point

Note the user performing the action is the staff member using the system (X-Okapi-User-Id?) rather than the users involved in any loan or request present.

May also need to perform similar checks when creating or updating a loan (using POST or PUT to the collection endpoints).