Limit event participants by email address

Once an event is set as private, there should be an additional option to restrict access based on specific email addresses.

This feature would allow event creators to define a list of approved participants. Only users with matching email addresses would be able to access and book the event. If an unauthorized user attempts to access it, they should receive a clear message indicating that the event is private and restricted and they should reach the owner and ask him to grant him access.

This capability would prevent invited participants from freely sharing the event link and would enable the creation of truly exclusive, access-controlled events.