Change variant fulfillment service to Shopify

[taylor-single]

So, to add a variant to be managed by a fulfillment service, you set the `fulfillment_service` property on the variant to the handle of the fulfillment service and update the variant.

How do we go in the opposite direction? If we want to return the item back to being managed by shopify fulfillment.

I've tried setting `inventory_management` to `shopify` but it seems to have no effect. Attempting to set `fulfillment_service` on the variant to `null` results in no effect. Setting it to an empty string results in:
```json
[{"errors":{"fulfillment_service":["can't be blank","is not defined for your shop"]}}]
```

[Luke_K · Accepted solution]

Hey @taylor-single 

Thanks for raising this! So going by what you've got,  I believe fulfillment service is expecting "manual" or alternatively the handle of the fulfillment service when you make that call and won't accept the empty string or null when passed into the fulfillment service in the REST API. It could be clearer in the documentation, I'll raise that internally!

By default on product variant creation, unless otherwise specified, the fulfillment_service would default to "manual" with the inventory_management set to "Shopify". By that premise,  If you're looking to set it back to Shopify still, I'm able to PUT to the product variant if I supply fulfillment_service": "manual" & "inventory_management" : "Shopify" in my PUT call. 

Does that work for you? Let me know, and if you're still running into issues, please supply me with a x-request_id from the headers and I can take a look into it. Thanks!

 Valid values: manual or the handle of a fulfillment service.