Create custom Field Type for Ticket

[mikemadison13]

This should be functionally similar to the paragraphs module in that it should be an entity reference field and should pull in the ticket type fields into the event (or whatever other node) so that they can be filled out during the referencing process. Note one key difference is that a ticket can only be used once (on a single event) so the field also needs to be contextually aware if the entities are valid for embedding.