Fix: Unknown service

A service with the identifier `application_module_mapper` is not registered. The required service should probably be `zfmodule_mapper_module`.

There is only one class in the entire project that implements a method `findByName()`, and that is `ZfModule\Mapper\Module`, of which an instance is returned when attempting to retrieve a service with the identifier `zfmodule_mapper_module`.

Came across this when working on injecting dependencies into the view helpers in the `User` module and my tests failed.