listOrders() returns http 500 status

[gothub]

Listing orders with GET `/bookkeeper/v1/orders' causes http 500 status to be returned, with the terse error msg:

{"code":500,"message":"Couldn't list orders: null"}

[gothub]

@csjx This error occurred at line https://github.com/DataONEorg/bookkeeper/blob/master/src/main/java/org/dataone/bookkeeper/resources/OrdersResource.java#L148 which should be changed to

            } else if ( subject != null && ! subject.isEmpty() ) {

However, listOrders needs to be refactored, as the following need to be provided:

• needs to return http 404 if order is not found when either subject or customerId is specified
  • currently returns empty order object
• needs to return http 403 if user isn't an admin user
  • currently returns empty order object

[gothub]

@csjx also, listOrders currently has the subject param, but does not have the requestor param that is documented at https://app.swaggerhub.com/apis/dataoneorg/bookkeeper/v1#/Orders/listOrders

[csjx]

Thanks @gothub - working on this now.

[csjx]

This is fixed. We had a null pointer exception in the call. I also refactored the pay() logic and the listOrders() logic to address the points above.