[oxura]

Fixes #541

Description

map_sqlx_error normalized unique constraint failures but left foreign key failures as backend errors. Saving a model with a missing referenced primary key therefore produced the wrong public error.

This adds DatabaseError::ForeignKeyViolation, maps SQLx's foreign-key classification to it, and covers the missing-parent insert through the model API.

Type of change

• Bug fix
• New feature
• Documentation
• Refactor / cleanup
• Performance improvement
• Other (describe above)

Validation

• cargo test -p cot --all-features --test db db_testing::relations::foreign_keys_sqlite -- --exact
• cargo test -p cot --all-features --test db (55 passed, 104 external-database tests ignored)
• cargo clippy --no-deps --all-targets -- -D warnings
• cargo fmt --all --check
• git diff --check upstream/master...HEAD

I did not run the ignored PostgreSQL/MySQL tests locally; those require the Docker Compose services and remain covered by CI.

Checklist

• I've read the contributing guide
• Tests pass locally (just test-all)
• Code passes clippy (just clippy)
• Code is properly formatted (cargo fmt)
• New tests added (regression test for bugs, coverage for new features)
• Documentation (both code and site) updated (if applicable)

[seqre]

Welcome to Cot and thank you for your contribution! One small fix and it should be okay to merge

[seqre]

It needs fixing with the addition of the new error, probably just this should be enough, but please test to ensure it works!

Suggested change

	assert!(matches!(error, DatabaseError::ForeignKeyViolation));

[oxura]

Updated. The delete-path assertion now expects ForeignKeyViolation. SQLite reports ON DELETE RESTRICT as SQLITE_CONSTRAINT_TRIGGER (1811), rather than its usual foreign-key code, so I extended the mapper for that exact code/message pair. The focused test and the full cot database test target pass.

[m4tx]

Looks good to me, thanks!