**What**
- validate that variants are unique with respect to options on product update/create and variant update/create
- validate that the product has options upon creation
- ensure variants have the same number of option values as the product has options
- admin error handling
- update tests
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FIXES FRMW-2707 CC-556
**What**
- Adds `metadata` to the default response for `/admin/collection` endpoints.
- Fixes tests to expect correct shape and not use objectContaining.
Fixes CC-551
