I get this error:

A new entity was found through the relationship 'AppEntityReseauxSociauxConversation#utilisateur1' that was not configured to cascade persist operations for entity: John_Doe. To solve this issue: Either explicitly call EntityManager#persist() on this unknown entity or configure cascade persist this association in the mapping for example @ManyToOne(..,cascade={"persist"}).

This is in my controller

    $conversation = new Conversation();
    $conversation->setUtilisateur1($user);
    $conversation->setUtilisateur2($otherUser);

    $this->entityManager->persist($conversation);
    $this->entityManager->flush();

This is in my entity conversation:

 class Conversation
    {
        ...
        /**
         * @ORMManyToOne(targetEntity=User::class, inversedBy="conversations")
         * 
         */
        private $utilisateur1;

        /**
        * @ORMManyToOne(targetEntity=User::class)
        */
        private $utilisateur2;
    }

Then I added cascade={"persist"} to my attribute utilisateur1 like this:

/**
* @ORMManyToOne(targetEntity=User::class, inversedBy="conversations", cascade={"persist"})
* 
*/
private $utilisateur1;

Then I get:

"An exception occurred while executing a query: SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '[email protected]' for key 'UNIQ_8D93D649E7927C74'"