Backorder flag applied incorrectly on PDP

[spencern]

Prerequisites

• Are you running the latest version?
• Are you able to consistently reproduce the issue?
• Did you search the issue queue for existing issue?

Issue Description

As an admin, when creating a new product, the backorder badge is applied incorrectly. As seen in this image, the backorder badge is visible on the variant while the quantity is > 0. It seems that the backorder badge is being applied when the low inventory badge should be applied as an admin.

The backorder badge is also applied incorrectly on the consumer view of the PDP:

This seems to happen when viewing a product where the allow backorder toggle is enabled and the Quantity is <= the number provided in the Warn at input on the PDP.

The Admin Product Grid displays the correct badge

The new catalog based product grid displays most badges correctly, but when Allow backorder is enabled, the Low inventory badge never displays. This is incorrect. The Low inventory badge should always show when the quantity is greater than 0, but less than or equal to the warn at number.

When the quantity is equal to 0, the badge shown should be Backorder if Allow backorder is enabled, or Sold out if not.

Steps to Reproduce

Please provide starting context, i.e. logged in as a user, configure a particular payment method.

1. Create a product
2. Set the Quantity to 5
3. Set the warn at number to 5
4. Ensure that Allow backorder is enabled

Possible Solution

My best guess is that we're not using the same logic/helper to determine which badge is shown in all spots. We should probably have a single component that calculates which badge is shown so that it's consistent and correct across the app.

Versions

Node: 8.9.0
NPM: 5.6.0
Meteor Node: 8.9.4
Meteor NPM: 5.6.0
Reaction CLI: 0.29.0
Reaction: 1.9.0
Reaction branch: master
Docker: 17.12.0-ce