Add optional soft delete support

[Sakura0122]

Pull Request

Discussion: #1890

Description

This follows up on #1890, which was closed due to inactivity.

This PR adds optional soft delete support with:

• SoftDeleteMixin, using deleted_at by default
• SoftDeleteSession.delete(), which marks soft-deletable models as deleted
• default filtering for SoftDeleteSession.exec(select(...))
• include_deleted=True to include soft-deleted rows
• custom soft delete field support with __soft_delete_field__

Compared with #1890, this keeps the change scoped to the soft delete feature and adds query filtering support.

Checklist

• This PR links to a GitHub Discussion for the proposed code change.
• I added tests for the change.
• The new or updated tests fail on the main branch and pass on this PR.
• Coverage stays at 100%.
• The documentation explains the change if needed.

[YuriiMotov]

Thanks for your interest!

We've recently updated contribution guidelines and PR description template, now we ask people not to open PRs unless maintainers explicitly ask to do it (see).

If you are interested in this feature being added to SQLMOdel, please open a discussion or find existing one and upvote\comment on it