Default value migration

[ariga]

Default value migration

[fishead]

@a8m patch is here #626, just let me known if it's not appropriate.
You are so friendly in the ent community.

[a8m]

Hey @fishead 👋

It should be fixed. Let me know if you want to contribute and I can guide you, or I can do it later today 🙏

[fishead]

I'm glad to make a PR.

[a8m]

Here's where we handle the default values:
https://github.com/ariga/atlas/blob/master/sql/mysql/inspect.go#L240
https://github.com/ariga/atlas/blob/master/sql/postgres/inspect.go#L181
https://github.com/ariga/atlas/blob/master/sql/sqlite/inspect.go#L141

We should use defaults.Valid instead of sqlx.ValidString. Just note that I added a commit (sqltest) in #622 to fix testing for it, so rebase and it's merged.

[a8m]

Fixed with #626. Thanks a lot @fishead