services.yml

parameters:
    app_schema: mon_super_schema
    
services:
    app_schema_prefixer_subscriber:
        class: App\EventSubscriber\TableSchemaSubscriber
        arguments: ['%app_schema%']
        tags:
            - { name: doctrine.event_subscriber }

TableSchemaSubscriber.php

<?php

namespace App\EventSubscriber;
use \Doctrine\ORM\Event\LoadClassMetadataEventArgs;
use Doctrine\Common\EventSubscriber;

class TableSchemaSubscriber implements EventSubscriber
{
    protected $schemaName = '';

    public function __construct($schemaName)
    {
        $this->schemaName = (string) $schemaName;
    }

    public function loadClassMetadata(LoadClassMetadataEventArgs $eventArgs)
    {
        $classMetadata = $eventArgs->getClassMetadata();

        if (!$classMetadata->isInheritanceTypeSingleTable() || $classMetadata->getName() === $classMetadata->rootEntityName) {
            $classMetadata->setPrimaryTable([
                'schema' => $this->schemaName
            ]);
        }
    }

    public function getSubscribedEvents() {
        return array('loadClassMetadata');
    }

}