2.5.x features

shows, show-schedules, show-preview, show-history-feed, item-history-feed endpoints to the HTTP api to be used via NewscoopAirtimePlugin

These endpoints are needed for airtime pro instances and should be merged to saas branch.
Mark, thanks for adding this function in and making $request a parameter.

I searched Airtime's codebase and this function was previously copied and pasted into 3 other spots (!):
PlayouthistoryController.php line 22
ShowbuilderController.php line 239
ListenerstatController.php line 13
and now ApiController.php line 1256

Please move this function (with the $request parameter) to common/DateHelper.php and remove the other occurrences of it. 

Additionally, we should not be passing requests around beyond the outer HTTP/service layer of Airtime. You can do your part here by splitting up the function into two parts:

(common/DateHelper.php)
public static function getStartEnd($endTimestamp, $startTimestamp)
{
....
}

(Create a new file, common/HTTPHelper.php) 
public static function getStartEndFromRequest($request)
{
      return getStartEnd($request->getParam("start"), $request->getParam("end"));
}