Method: Returns the meta key relating an Attendee to a User.

Method: Returns an array of the attendee types handled by this repository.

Method: Returns the list of meta keys relating an Attendee to a Post (Event).

Method: Filters events to include only those that match the provided RSVP state.

Method: Filters events that have a ticket with a specific cost currency symbol.

Method: Filters events to include only those that match the provided ticket state.