The driver and BSON library are currently configured to use the 2018 edition of Rust. The 2021 one was released in version 1.56.0, which is earlier than our MSRV, so we should be safe to upgrade.

For more information on what editions are, what upgrading them entails, and what's in the 2021 edition, see https://doc.rust-lang.org/edition-guide/introduction.html. The important thing to note is that upgrading editions will not affect our users in any way.