fix(core): Add field resolver for Order.shippingLines

Relates to #2859

packages/core/src/api/resolvers/entity/order-entity.resolver.ts

@@ -63,6 +63,17 @@ export class OrderEntityResolver {
         return lines;
     }
 
+    @ResolveField()
+    async shippingLines(@Ctx() ctx: RequestContext, @Parent() order: Order) {
+        if (order.shippingLines) {
+            return order.shippingLines;
+        }
+        const { shippingLines } = await assertFound(
+            this.orderService.findOne(ctx, order.id, ['shippingLines.shippingMethod']),
+        );
+        return shippingLines;
+    }
+
     @ResolveField()
     async history(
         @Ctx() ctx: RequestContext,