feat: Provisionner automatiquement un nouvel établissement

Lorsqu'un super-admin crée un établissement via l'interface, le système
doit automatiquement créer la base tenant, exécuter les migrations,
créer le premier utilisateur admin et envoyer l'invitation — le tout
de manière asynchrone pour ne pas bloquer la réponse HTTP.

Ce mécanisme rend chaque établissement opérationnel dès sa création
sans intervention manuelle sur l'infrastructure.

backend/tests/Unit/Shared/Infrastructure/Tenant/DoctrineTenantRegistryTest.php

@@ -0,0 +1,119 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Unit\Shared\Infrastructure\Tenant;
+
+use App\Shared\Infrastructure\Tenant\DoctrineTenantRegistry;
+use App\Shared\Infrastructure\Tenant\TenantId;
+use App\Shared\Infrastructure\Tenant\TenantNotFoundException;
+use Doctrine\DBAL\Connection;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+
+#[CoversClass(DoctrineTenantRegistry::class)]
+final class DoctrineTenantRegistryTest extends TestCase
+{
+    private const string MASTER_URL = 'postgresql://classeo:secret@db:5432/classeo_master';
+    private const string TENANT_ID = 'a1b2c3d4-e5f6-7890-abcd-ef1234567890';
+    private const string SUBDOMAIN = 'ecole-alpha';
+    private const string DB_NAME = 'classeo_tenant_a1b2c3d4e5f67890abcdef1234567890';
+
+    #[Test]
+    public function itResolvesConfigBySubdomain(): void
+    {
+        $registry = $this->registryWith([
+            ['tenant_id' => self::TENANT_ID, 'subdomain' => self::SUBDOMAIN, 'database_name' => self::DB_NAME],
+        ]);
+
+        $config = $registry->getBySubdomain(self::SUBDOMAIN);
+
+        self::assertSame(self::SUBDOMAIN, $config->subdomain);
+        self::assertSame(self::TENANT_ID, (string) $config->tenantId);
+        self::assertSame('postgresql://classeo:secret@db:5432/' . self::DB_NAME, $config->databaseUrl);
+    }
+
+    #[Test]
+    public function itResolvesConfigByTenantId(): void
+    {
+        $registry = $this->registryWith([
+            ['tenant_id' => self::TENANT_ID, 'subdomain' => self::SUBDOMAIN, 'database_name' => self::DB_NAME],
+        ]);
+
+        $config = $registry->getConfig(TenantId::fromString(self::TENANT_ID));
+
+        self::assertSame(self::SUBDOMAIN, $config->subdomain);
+    }
+
+    #[Test]
+    public function itThrowsForUnknownSubdomain(): void
+    {
+        $registry = $this->registryWith([]);
+
+        $this->expectException(TenantNotFoundException::class);
+        $registry->getBySubdomain('inexistant');
+    }
+
+    #[Test]
+    public function itThrowsForUnknownTenantId(): void
+    {
+        $registry = $this->registryWith([]);
+
+        $this->expectException(TenantNotFoundException::class);
+        $registry->getConfig(TenantId::fromString(self::TENANT_ID));
+    }
+
+    #[Test]
+    public function itChecksExistence(): void
+    {
+        $registry = $this->registryWith([
+            ['tenant_id' => self::TENANT_ID, 'subdomain' => self::SUBDOMAIN, 'database_name' => self::DB_NAME],
+        ]);
+
+        self::assertTrue($registry->exists(self::SUBDOMAIN));
+        self::assertFalse($registry->exists('inexistant'));
+    }
+
+    #[Test]
+    public function itReturnsAllConfigs(): void
+    {
+        $registry = $this->registryWith([
+            ['tenant_id' => self::TENANT_ID, 'subdomain' => self::SUBDOMAIN, 'database_name' => self::DB_NAME],
+            ['tenant_id' => 'b2c3d4e5-f6a7-8901-bcde-f12345678901', 'subdomain' => 'ecole-beta', 'database_name' => 'classeo_tenant_beta'],
+        ]);
+
+        $configs = $registry->getAllConfigs();
+
+        self::assertCount(2, $configs);
+    }
+
+    #[Test]
+    public function itQueriesDatabaseOnlyOnce(): void
+    {
+        $connection = $this->createMock(Connection::class);
+        $connection->expects(self::once())
+            ->method('fetchAllAssociative')
+            ->willReturn([
+                ['tenant_id' => self::TENANT_ID, 'subdomain' => self::SUBDOMAIN, 'database_name' => self::DB_NAME],
+            ]);
+
+        $registry = new DoctrineTenantRegistry($connection, self::MASTER_URL);
+
+        $registry->getBySubdomain(self::SUBDOMAIN);
+        $registry->getConfig(TenantId::fromString(self::TENANT_ID));
+        $registry->exists(self::SUBDOMAIN);
+        $registry->getAllConfigs();
+    }
+
+    /**
+     * @param array<array{tenant_id: string, subdomain: string, database_name: string}> $rows
+     */
+    private function registryWith(array $rows): DoctrineTenantRegistry
+    {
+        $connection = $this->createMock(Connection::class);
+        $connection->method('fetchAllAssociative')->willReturn($rows);
+
+        return new DoctrineTenantRegistry($connection, self::MASTER_URL);
+    }
+}