M1: key management, backup locations and occ commands

- migration: ngb_targets, ngb_runs, ngb_snapshots
- KeyService: master key stored encrypted with the instance secret
  (unattended backups), passphrase-wrapped copy in every repository and
  in the recovery kit, recorded admin confirmation per key fingerprint
- TargetService: locations built from files_external backends without a
  mount; files_external is loaded through IAppManager::loadApp() and its
  enabled state is left alone; credentials encrypted with ICrypto;
  existing repositories are adopted only if made with this key, and a
  repository cannot be registered twice
- Repository: initWithKey/openWithKey with an encrypted key check
- occ: backup:key:init|kit|confirm, backup:target:backends|add|list|remove

lib/Service/TargetService.php

@@ -0,0 +1,124 @@
+<?php
+
+declare(strict_types=1);
+
+// SPDX-FileCopyrightText: 2026 Dillard Blom
+// SPDX-License-Identifier: AGPL-3.0-or-later
+
+namespace OCA\NgBackup\Service;
+
+use OCA\NgBackup\Backend\ExternalStorageFactory;
+use OCA\NgBackup\Backend\IBackend;
+use OCA\NgBackup\Backend\StorageBackend;
+use OCA\NgBackup\Db\Target;
+use OCA\NgBackup\Db\TargetMapper;
+use OCA\NgBackup\Repository\Repository;
+use OCP\App\IAppManager;
+use OCP\Security\ICrypto;
+use OCP\Server;
+
+/**
+ * Backup targets: a files_external backend + auth mechanism + options + base path. The storage
+ * object is built only while it is used; nothing is mounted. files_external is loaded for its
+ * classes but its enabled/disabled state is left as the admin set it.
+ */
+class TargetService {
+	public function __construct(
+		private TargetMapper $mapper,
+		private KeyService $keys,
+		private ICrypto $crypto,
+		private IAppManager $appManager,
+	) {
+	}
+
+	/** @return list<array{id:string, name:string, auth:list<string>, parameters:array}> */
+	public function availableBackends(): array {
+		return $this->factory()->describeBackends();
+	}
+
+	/**
+	 * Add a target: connect, create the repository there (or adopt an existing one made with this
+	 * installation's key), then save it.
+	 *
+	 * @param array<string, mixed> $options
+	 * @return array{target: Target, created: bool}
+	 */
+	public function add(string $name, string $backend, string $auth, array $options, string $basePath): array {
+		if (!preg_match('/^[A-Za-z0-9][A-Za-z0-9 _.-]{0,63}$/', $name)) {
+			throw new \InvalidArgumentException('Name: letters, digits, space, _ . - (max 64)');
+		}
+		try {
+			$this->mapper->findByName($name);
+			throw new \InvalidArgumentException("A target named '$name' already exists");
+		} catch (\OCP\AppFramework\Db\DoesNotExistException) {
+		}
+		$keys = $this->keys->keyRing();
+		$storageBackend = $this->buildBackend($backend, $auth, $options, $basePath);
+		if ($storageBackend->exists('config')) {
+			$repo = Repository::openWithKey($storageBackend, $keys);
+			$created = false;
+		} else {
+			$repo = Repository::initWithKey($storageBackend, $keys, $this->keys->wrappedKey());
+			$created = true;
+		}
+
+		foreach ($this->mapper->findAll() as $existing) {
+			if ($existing->getRepositoryId() === $repo->id()) {
+				throw new \InvalidArgumentException("This repository is already registered as '{$existing->getName()}'");
+			}
+		}
+
+		$target = new Target();
+		$target->setName($name);
+		$target->setBackend($backend);
+		$target->setAuth($auth);
+		$target->setOptions($this->crypto->encrypt(json_encode($options, JSON_THROW_ON_ERROR)));
+		$target->setBasePath(trim($basePath, '/'));
+		$target->setRepositoryId($repo->id());
+		$target->setCreatedAt(time());
+		return ['target' => $this->mapper->insert($target), 'created' => $created];
+	}
+
+	/** @return list<Target> */
+	public function list(): array {
+		return $this->mapper->findAll();
+	}
+
+	public function get(string $nameOrId): Target {
+		return ctype_digit($nameOrId) ? $this->mapper->find((int)$nameOrId) : $this->mapper->findByName($nameOrId);
+	}
+
+	/** Remove the target from NG Backup. The backups on the target itself are not touched. */
+	public function remove(Target $target): void {
+		$this->mapper->delete($target);
+	}
+
+	public function backend(Target $target): IBackend {
+		return $this->buildBackend($target->getBackend(), $target->getAuth(), $this->options($target), $target->getBasePath());
+	}
+
+	public function repository(Target $target): Repository {
+		$repo = Repository::openWithKey($this->backend($target), $this->keys->keyRing());
+		if ($target->getRepositoryId() !== null && $repo->id() !== $target->getRepositoryId()) {
+			throw new \RuntimeException('The target now contains a different repository than when it was added');
+		}
+		return $repo;
+	}
+
+	/** @return array<string, mixed> */
+	public function options(Target $target): array {
+		return json_decode($this->crypto->decrypt($target->getOptions()), true, 512, JSON_THROW_ON_ERROR);
+	}
+
+	private function buildBackend(string $backend, string $auth, array $options, string $basePath): StorageBackend {
+		return new StorageBackend($this->factory()->create($backend, $auth, $options), $basePath);
+	}
+
+	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');
+		}
+		return new ExternalStorageFactory(Server::get(\OCA\Files_External\Service\BackendService::class));
+	}
+}