CALENDAR: Add an option to schedule appointments not linked to any user.

Affected Users:
Secretaries and administrators.

Task Affected:
Creating appointments without assigning a provider immediately, so that a provider can be linked at a later time.

Impact:
Currently, users must create the appointment under a placeholder (fake) user or assign it to a real user. This can make it difficult for the actual provider to locate the appointment later, and may cause confusion among staff.

Current State:
Appointments are created in a placeholder user’s calendar. Users must then manually send tasks or messages to notify staff where to find the appointment and which provider will eventually see the patient.

Competition Consideration:
N/A