Add unit test that prevents branching db migrations

test/db/test_migrations.py

+import pytest
+from alembic.migration import MigrationContext
+from sqlalchemy import create_engine
+
+
+@pytest.mark.noautofixt()
+def test_migrations_no_branches(db_uri):
+    engine = create_engine(db_uri)
+    conn = engine.connect()
+    context = MigrationContext.configure(conn)
+
+    assert len(context.get_current_heads()) == 1, (
+        "\n\n!!!\n\nDetected a branching of db migrations. This is caused by multiple `down_revision`s referring to the"
+        " same migration.\n\nPlease resolve this by updating either one of these migrations: "
+        f"{context.get_current_heads()}.\n\n!!!\n\n"
+    )

tox.ini

@@ -13,7 +13,7 @@ deps =
     -r requirements.txt
 
 commands =
-    ruff --respect-gitignore --preview .
+    ruff check --respect-gitignore --preview .
     ruff format --respect-gitignore --preview --check .
     mypy .
     coverage erase