The database layer in our example is implemented with the Doobie library. Its official website describes it as a pure functional JDBC layer for Scala and Cats. It allows us to abstract existing JDBC functionality in a nice functional way. Let's show how this is done. The library can be found at https://tpolecat.github.io/doobie/. In the following examples, please assume the following imports to be in scope:
import cats.effect.IOimport fs2.Streamimport doobie._import doobie.implicits._import doobie.util.transactor.Transactorimport cats.implicits._
We also need some model classes to persist, and for the purpose of the example, we'll keep the ADT as small as possible:
object Model { type Inventory = Map
