You will need a 'Rocket.toml' file so Rocket can find your MariaDB. It should look something like this:
[global.databases]
my_db = { url = "mysql://user:password@host/database"}
my_db is a name used in the Rust code.
If you change it in your Rocket.toml,
you have to change it in the code too.
You will also need a '.env' file for the diesel command line tool.
It should look something like this:
DATABASE_URL=mysql://user:password@host/database