Foreign key support in SQLite

[foldu]

If you want to use foreign keys in SQLite you need to enable them with PRAGMA FOREIGN KEYS = ON; on every new connection (see Section 2 of https://sqlite.org/foreignkeys.html).
It would be nice if sqlx's Pool had support for automatically doing this when it establishes a new connection.

[mehcode]

@foldu Definitely agree the Pool needs something generic to handle doing stuff on lifecycle events.

---

Pool::builder()
  .on_connect(|conn: &mut C| { async move {
    // [...]
  }})
  .build()

I could imagine on_connect, on_acquire, on_release. Does this setup feel fine?

---

The other option is we could support a URL parameter for some pragmas like foreign_keys. E.g., sqlite://a.db?foreign_keys=on.

Thoughts? We definitely need the Pool hooks but this might be better for your specific case.

[mehcode]

This is now on by default (because yes) and there is a foreign_keys option in SqliteConnectOptions