Notify board members about moved cards according to their Deck setting

Replaces the yes/no notify_email flag with notify_mode:
- off:   no mail
- owner: only the board owner, as before (migrated from notify_email=1)
- board: everyone with access to the board, filtered by their own Deck
         "Notifications" setting for it (board:<id>:notify-due: off /
         assigned / all), mirroring Deck's NotificationHelper rules

Recipients are resolved via PermissionService::findUsers() (owner, ACL,
groups and circles expanded), AssignmentMapper::isUserAssigned() and
IConfig, none of which reads Deck's frozen $userId. If they cannot be
resolved, no mail is sent rather than one to the wrong people.

Moved cards are collected over the whole run and each recipient gets a
single digest mail afterwards, in their own language.

Bumps to 35.2.0 so the migrations run.

lib/Service/DeckIntegrationService.php

@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace OCA\WorkflowDeckAutomation\Service;
 
+use OCA\Deck\Db\AssignmentMapper;
 use OCA\Deck\Db\BoardMapper;
 use OCA\Deck\Db\Card;
 use OCA\Deck\Db\CardMapper;
@@ -14,6 +15,7 @@ use OCA\Deck\Service\PermissionService;
 use OCA\Deck\Service\StackService;
 use OCP\App\IAppManager;
 use OCP\AppFramework\Db\DoesNotExistException;
+use OCP\IConfig;
 use OCP\IUser;
 use OCP\Server;
 use Psr\Log\LoggerInterface;
@@ -66,6 +68,7 @@ class DeckIntegrationService {
 
 	public function __construct(
 		private IAppManager $appManager,
+		private IConfig $config,
 		private LoggerInterface $logger,
 	) {
 	}
@@ -302,6 +305,81 @@ class DeckIntegrationService {
 		return $owner;
 	}
 
+	/**
+	 * Who should hear about each of the given (moved) cards, according to
+	 * every board member's own Deck notification setting for this board —
+	 * the "Notifications: none / assigned cards / all cards" menu, stored as
+	 * the user preference `deck` / `board:<id>:notify-due`. The decision
+	 * itself is NotificationPolicy::shouldNotify(), a copy of Deck's rules.
+	 *
+	 * Like findStackIds(), assembled only from pieces that take the users
+	 * explicitly and never consult Deck's frozen `$userId`:
+	 * PermissionService::findUsers() reads the owner and ACL through mappers
+	 * and expands groups and circles itself; AssignmentMapper is a plain
+	 * mapper that also resolves group/circle assignments; the preference is
+	 * read straight from IConfig.
+	 *
+	 * Throws on any failure, so the caller can log and skip the mail instead
+	 * of mailing a half-resolved or wrong set of people.
+	 *
+	 * @param int[] $cardIds
+	 * @return array<int, list<string>> card id => uids to notify
+	 * @throws DeckUnavailableException
+	 */
+	public function findNotificationRecipients(int $boardId, array $cardIds): array {
+		try {
+			$board = $this->resolve(BoardMapper::class)->find($boardId, false, true);
+			$owner = $this->unwrapUid($board->getOwner());
+			// Deck notifies the owner of a board nobody else can see about
+			// every card: "assigned" means nothing there.
+			$unshared = count($board->getAcl() ?? []) === 0;
+
+			// `true` bypasses PermissionService's per-process cache, which
+			// would otherwise outlive ACL changes for the whole cron pass.
+			$participants = $this->resolve(PermissionService::class)->findUsers($boardId, true);
+			$assignments = $this->resolve(AssignmentMapper::class);
+
+			$settings = [];
+			foreach ($participants as $uid => $participant) {
+				// Users of other instances (FederatedUser) have no local
+				// account and no preference to read.
+				if (!is_a($participant, 'OCA\Deck\Db\User')) {
+					continue;
+				}
+				// Numeric uids come back as integer array keys.
+				$uid = (string)$uid;
+				$settings[$uid] = (string)$this->config->getUserValue(
+					$uid,
+					self::DECK_APP_ID,
+					'board:' . $boardId . ':notify-due',
+					NotificationPolicy::DECK_DEFAULT,
+				);
+			}
+
+			$recipients = [];
+			foreach ($cardIds as $cardId) {
+				$recipients[$cardId] = [];
+				foreach ($settings as $uid => $setting) {
+					$uid = (string)$uid;
+					$notify = NotificationPolicy::shouldNotify(
+						$setting,
+						$unshared && $uid === $owner,
+						static fn (): bool => (bool)$assignments->isUserAssigned($cardId, $uid),
+					);
+					if ($notify) {
+						$recipients[$cardId][] = $uid;
+					}
+				}
+			}
+		} catch (DeckUnavailableException $e) {
+			throw $e;
+		} catch (Throwable $e) {
+			throw new DeckUnavailableException('Could not resolve notification recipients for board ' . $boardId . ': ' . $e->getMessage(), 0, $e);
+		}
+
+		return $recipients;
+	}
+
 	/**
 	 * Deck's own exception classes are referenced by name: `is_a()` with a
 	 * string simply returns false when the class does not exist, so a missing
@@ -368,9 +446,10 @@ class DeckIntegrationService {
 	public function getActiveCardsInStack(int $stackId): array {
 		return $this->call(function () use ($stackId) {
 			// Deliberately not enriched: CardService::enrichCards() only adds
-			// labels, assignees and comment counts — none of which is used —
-			// and runs BoardService::find(), a permission check against
-			// Deck's frozen uid (see beginUserContext()).
+			// labels, assignees and comment counts, and runs
+			// BoardService::find(), a permission check against Deck's frozen
+			// uid (see beginUserContext()). Assignments, where needed for
+			// mails, come from findNotificationRecipients() instead.
 			$cards = $this->resolve(CardMapper::class)->findAllByStack($stackId);
 
 			return array_values(array_filter($cards, static function (Card $card) {