Diesel DB calls are blocking

[jaythomas]

Feedback received from Reddit user Hersenbeuker:

You're using blocking Diesel database calls: https://github.com/codi-hacks/weather-station/blob/master/api-server/src/sensors/routes.rs#L16

This blocks the async runtime, you have to use the actix block functions to move these calls to the actix threadpool: https://actix.rs/docs/databases/