OrderDetailComponent not handling all ErrorResults from addFulfillmentToOrder

[michaelbromley]

Describe the bug
In the Admin UI, when creating a fulfillment, not all the possible ErrorResult types are being handled in the UI code. For example, CreateFulfillmentError is silently ignored.

The code in question is here:

vendure/packages/admin-ui/src/lib/order/src/components/order-detail/order-detail.component.ts

Lines 335 to 344 in fce00c4

	switch (result.addFulfillmentToOrder.__typename) {
	case 'Fulfillment':
	this.notificationService.success(_('order.create-fulfillment-success'));
	break;
	case 'EmptyOrderLineSelectionError':
	case 'InsufficientStockOnHandError':
	case 'ItemsAlreadyFulfilledError':
	this.notificationService.error(result.addFulfillmentToOrder.message);
	break;
	}

To Reproduce
Steps to reproduce the behavior:

1. Create a FulfillmentHandler which throws an error
2. Attempt a fulfillment with that handler
3. No error feedback in the UI

Expected behavior
Display error notification for all error types. We should add an assertNever clause as an exhaustiveness check here.

Environment (please complete the following information):

• @vendure/core version: 1.0.2
• Nodejs version: any
• Database (mysql/postgres etc): any