Changes to List all visitors

added the enum value first_name to the property items/ of the query request parameter fields

added the enum value last_name to the property items/ of the query request parameter fields

added the optional property items/first_name to the response with the 200 status

added the optional property items/last_name to the response with the 200 status

the response's body type changed from no type to array for status 200

the response's body type changed from array to no type for status 200