Move from Diesel to SQLx?

[dbrgn]

https://github.com/launchbadge/sqlx

SQLx is not an ORM, it's more lightweight than Diesel. It provides slightly less static guarantees than Diesel, but still does compile-time verification of queries. (Note: I'm not sure how robust the offline mode is, we don't want to require a database just to compile the project.)

Main advantage is that it's async, so it integrates better with Rocket.