Returns a list of all assigned Knowledge Card Contents at any level for a specified User. If User's assinged content has no active knowledge card at any level, an empty array is returned. Each Knowledge Card returned will contain the Knowledge Card Draft Id, Id, Language Id, identifier, the article which contains contents of Knowledge card and the Knowledge Card Draft Object. Knowledge Card Draft object describes the Mastery object type and Mastery object Id that it is associated with. If a User ID is not provided then it will return the results for the authenticated User ID.