Design pattern Doctrine ORM - Generate unique names based on input - php

Question

I am working with Symfony2 and Doctrine ORM and want to achieve the following with a clean architecture :
Each time a new Entity is created, I want to save a "display name" chosen by my end-user, then generate a "unique name" based on the "display name".
If my end-user want to create 3 Project called "Drawings",
the first one will have display_name = "drawings"
the second one will have display_name = "drawings2"
the third one will have display_name = "drawings3"
(or something like that, whatever the pattern)
Basic Entity example :
/**
* Project.
*
* #ORM\Entity
*/
class Project
{
//...
/**
* #ORM\Column(type="string", length=50, nullable=false)
*/
protected $name_display ;
/**
* #ORM\Column(type="string", length=50, nullable=false, unique=true)
*/
protected $name_unique ;
//...
Basic usage example :
$project = new Project();
$project->setDisplayName('Drawings');
//Around here I would like the Unique name to be generated
$this->getDoctrine()->getManager()->persist($project);
I thought about various solutions :
Doing the name generation in the Controller, but it's not re-usable
Doing the unique name generation in the repository. But it seem to be a bad practive (repositories should be read-only)
Using a PrePersist LifecycleCallbacks from doctrine, but it's not a good practice as I need the Entity Manager to do a Database
Doing the name generation in the Entity Setter, injecting the Entity Manager to make requests and look for available names. That looks horrible
Using a service to persist the Entity as explained here : Are Doctrine2 repositories a good place to save my entities? (But it's quite complicated and involve a huge change in my infrastructure if I want to have all my Entity creations to be consistent with this practice)

Answer 1

I would recommend the last options - services. It may need changes in your project, but I find this the best way to manage usual crud operations with entities - create, save, findBySomething ...
It is crystal clear - no black magic. As opposed to events where there is no obvious relation between the executed code and actions with entities (like creating it through new).
It is not dependent on annotations and it is easy to maintain.
Controllers and other services may access this service through Dependency Injection which is a clear way of satisfying dependencies of business objects(objects holding business logic)
Your repositories won't become bigger and bigger
You can use default repositories - fewer issues with back compatibility when upgrading Doctrine
It is much better than the "setter solution", which sounds really horrible - entities should never be that mighty, so they would have references to services (especially services like EntityManager)