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TNL-291

@andy-armstrong @cahrens please review.

@talbs thanks for the front-end work :smile: 

@explorerleslie would you like me to create a sandbox?
@andy-armstrong - Just to alert you - if the second argument to `$.extend()` has an undefined field, that field does not get joined into the target object. None of our tests failed, but this behavior does differ from the previous, so I thought I'd bring it up.