[RFC]: Call repositories via the services in handlers

[alexmerlin]

RFC

Instead of using:

ExampleHandler.php:

public function handle(ServerRequestInterface $request): ResponseInterface
{
    $entity = $handler->exampleService->findOneBy($params);
    // ...
}

ExampleService.php:

public function findOneBy(array $params): Example
{
    return $this->exampleRepository->findOneBy($params);
}

we should use:

ExampleHandler.php:

public function handle(ServerRequestInterface $request): ResponseInterface
{
    $entity = $handler->exampleService->getExampleRepository()->findOneBy($params);
    // ...
}

This way we would simplify a lot the existing services and could drop tons of service methods that have a single purpose of receiving request params from the handler and returning the data provided by the repository.

[alexmerlin]

Implemented in #396