Where database models are solely dedicated to be a representation of a database table you will also want to create business logic modules in order to keep your controllers clean. As a general good coding practice you should not put everything into your controllers. Business logic can be placed in modules. Modules are basically classes that are autoloaded during application bootstrap process. Then you just need use the class as how you wish. Modules are placed inside the modules directory. The file name must equal the class name.
In order to create a new module you can use the console:
php asatru make:module name
This will create a base structure class file in:
/app/modules/name.php
It will contain the following code:
<?php
/*
Asatru PHP - Module
*/
/**
* This class represents your module
*/
class ExampleModule {
}
Now you can implement your business logic there.