Datasource sanity checker

[TheRustifyer]

This issue aims to provide a procedural way of testing the status of the datasources in the canyon.toml config file.

This will let the user check the correctness of it's datasources within its source code, before starting to query the specified databases. Also, we can provide a macro parameter in canyon_macros::canyon that will make this check even at compile time, refusing to compile the client's program if the datasources aren't able to reach the targeted database