M5: end-to-end test matrix and CI

- tests/integration/roundtrip.sh: key, kit code and confirmation,
  location, full and unchanged incremental backup, restore new-folder and
  replace (files identical, extra file in the trash), database dump and
  restore, retention, trash and restore from trash, no files_external
  errors in the log
- tests/integration/matrix.sh: fresh Nextcloud per version and database
  (SQLite, MariaDB, PostgreSQL), removes only its own containers and
  their volumes; locally green on NC32 and NC35 with all three databases
- GitHub Actions: unit tests on PHP 8.2-8.4, round trip on NC32-35 x
  SQLite/MariaDB/PostgreSQL

Fixes found by the matrix:
- files_external is no longer booted when it is disabled: only its
  classes are loaded and a private BackendService gets its backends from
  its Application class (booting registered its mount provider, which
  failed on installations where its tables were never created)
- SQLite: the database file is excluded from the file backup (it is
  covered by the logical dump and copying the live file is inconsistent)
- occ backup:key:confirm accepts --code and --confirm for scripts

lib/Service/BackupService.php

@@ -218,6 +218,15 @@ class BackupService {
 			'data/*/cache',
 			'data/*/uploads',
 		];
+		// SQLite: the database file is in the data directory; it is backed up by the logical dump,
+		// and copying the live file would give an inconsistent copy.
+		if ($this->config->getSystemValueString('dbtype') === 'sqlite3') {
+			$dbName = $this->config->getSystemValueString('dbname', 'owncloud');
+			$exclude[] = "data/$dbName.db";
+			$exclude[] = "data/$dbName.db-journal";
+			$exclude[] = "data/$dbName.db-wal";
+			$exclude[] = "data/$dbName.db-shm";
+		}
 		$logFile = $this->config->getSystemValueString('logfile', '');
 		if ($logFile !== '' && str_starts_with($logFile, $dataDir . '/')) {
 			$exclude[] = 'data/' . substr($logFile, strlen($dataDir) + 1);

lib/Service/TargetService.php

@@ -121,11 +121,33 @@ class TargetService {
 		return new StorageBackend($this->factory()->create($backend, $auth, $options), $basePath);
 	}
 
+	private ?ExternalStorageFactory $factory = null;
+
+	/**
+	 * files_external's connection code, without changing the app's state:
+	 * - enabled: it is booted by Nextcloud; use its own BackendService;
+	 * - disabled: do NOT boot it (booting registers its mount provider and listeners, which use
+	 *   its database tables; on installations where it was never enabled those do not exist).
+	 *   Only its classes are loaded, and a private BackendService gets its backends and auth
+	 *   mechanisms from its Application class.
+	 */
 	private function factory(): ExternalStorageFactory {
-		// Load files_external's classes without enabling the app (its state stays as the admin set it).
-		if (!class_exists(\OCA\Files_External\Service\BackendService::class)) {
-			$this->appManager->loadApp('files_external');
+		if ($this->factory !== null) {
+			return $this->factory;
 		}
-		return new ExternalStorageFactory(Server::get(\OCA\Files_External\Service\BackendService::class));
+		if ($this->appManager->isEnabledForAnyone('files_external')) {
+			$this->appManager->loadApp('files_external');
+			return $this->factory = new ExternalStorageFactory(Server::get(\OCA\Files_External\Service\BackendService::class));
+		}
+		if (!class_exists(\OCA\Files_External\AppInfo\Application::class)) {
+			$path = $this->appManager->getAppPath('files_external');
+			require_once $path . '/composer/autoload.php';
+		}
+		$service = new \OCA\Files_External\Service\BackendService(
+			Server::get(\OCP\IAppConfig::class), Server::get(\Psr\Log\LoggerInterface::class));
+		$app = new \OCA\Files_External\AppInfo\Application();
+		$service->registerBackendProvider($app);
+		$service->registerAuthMechanismProvider($app);
+		return $this->factory = new ExternalStorageFactory($service);
 	}
 }