Method: Constructor for this class and the traits it uses.

Method: Retrieve courses associated with the membership

Method: Performs a WPDB query to retrieve posts associated with the membership

Method: Retrieve a list of posts associated with the membership

Method: Retrieve membership tags.

Method: Add data to the membership model when converted to array.

Method: Retrieve membership categories.

Method: Retrieve the number of enrolled students in the membership.

Method: Get the URL to a WP Page or Custom URL when sales page redirection is enabled