Support self-referencing FKs in `Table.create`

[numist]

---

:books: Documentation preview :books:: https://sqlite-utils--537.org.readthedocs.build/en/537/

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (c0251cc) 96.25% compared to head (a75abeb) 96.25%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #537 +/- ## ======================================= Coverage 96.25% 96.25% ======================================= Files 6 6 Lines 2671 2673 +2 ======================================= + Hits 2571 2573 +2 Misses 100 100 ``` | [Impacted Files](https://codecov.io/gh/simonw/sqlite-utils/pull/537?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Simon+Willison) | Coverage Δ | | |---|---|---| | [sqlite\_utils/db.py](https://codecov.io/gh/simonw/sqlite-utils/pull/537?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Simon+Willison#diff-c3FsaXRlX3V0aWxzL2RiLnB5) | `97.33% <100.00%> (+<0.01%)` | :arrow_up: | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Simon+Willison). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=Simon+Willison)

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[simonw]

Thanks!

[simonw]

Here's an example from the new tests:

https://github.com/simonw/sqlite-utils/blob/a75abeb61b91a28650d3b9933e7ec80ad0d92529/tests/test_create.py#L291-L307