Support self-referencing FKs in Table.create

[numist]

---

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

[codecov]

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

@@           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	Coverage Δ
sqlite_utils/db.py	97.33% <100.00%> (+<0.01%)	⬆️

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[simonw]

Thanks!

[simonw]

Here's an example from the new tests:

sqlite-utils/tests/test_create.py

Lines 291 to 307 in a75abeb

	def test_self_referential_foreign_key(fresh_db):
	assert [] == fresh_db.table_names()
	table = fresh_db.create_table(
	"test_table",
	columns={
	"id": int,
	"ref": int,
	},
	pk="id",
	foreign_keys=(("ref", "test_table", "id"),),
	)
	assert (
	"CREATE TABLE [test_table] (\n"
	" [id] INTEGER PRIMARY KEY,\n"
	" [ref] INTEGER REFERENCES [test_table]([id])\n"
	")"
	) == table.schema