defaultVariantId not set on initial save

[engram-design]

Description

Refer to craftcms/feed-me#493, but creating a brand new Product with multiple Variants, doesn't seem to set its defaultVariantId value. Subsequently re-saving the product will fix it right up. I'm ensuring that at least one variant has the 'default' switch on (near the matrix-like actions on the right-hand side).

I imagine its to do with the implementation here, where you're indeed sending an SQL update to correctly update the product - but it'll do nothing if the variant has null for an ID - which is what happens for a new variant.

I can see shortly after this code you're saving the variant. Would it be prudent to move this SQL update after the variant has been saved, therefore has an ID?

Additional info

• Craft version: 3.1.17
• PHP version: 7.0.31
• Database driver & version: MySQL
• Plugins & versions: Commerce 2.1.0.2

[lukeholder]

Thanks!