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/NotificationPolicy.php

@@ -0,0 +1,70 @@
+<?php
+
+declare(strict_types=1);
+
+namespace OCA\WorkflowDeckAutomation\Service;
+
+/**
+ * Who gets a mail about a moved card — pure logic, no Nextcloud or Deck
+ * dependencies, so it is unit-testable like WorkflowRunner::isOverdue().
+ */
+class NotificationPolicy {
+	/** No mail at all. */
+	public const MODE_OFF = 'off';
+	/** Only the workflow's owner (the board owner), regardless of Deck settings. */
+	public const MODE_OWNER = 'owner';
+	/** Everyone with access to the board, filtered by their own Deck setting. */
+	public const MODE_BOARD = 'board';
+
+	public const MODES = [self::MODE_OFF, self::MODE_OWNER, self::MODE_BOARD];
+
+	/**
+	 * Values of Deck's per-user, per-board preference
+	 * `deck` / `board:<boardId>:notify-due` (Deck's
+	 * ConfigService::SETTING_BOARD_NOTIFICATION_DUE_*), inlined so a renamed
+	 * constant cannot fatal this app. It is the board's "Notifications" menu
+	 * in Deck — the due-date reminder setting, which is exactly what fits a
+	 * card being moved because it fell due.
+	 */
+	public const DECK_OFF = 'off';
+	public const DECK_ASSIGNED = 'assigned';
+	public const DECK_ALL = 'all';
+	/** What Deck assumes for a user who never touched the setting. */
+	public const DECK_DEFAULT = self::DECK_ASSIGNED;
+
+	public static function isValidMode(string $mode): bool {
+		return in_array($mode, self::MODES, true);
+	}
+
+	/**
+	 * Mirrors Deck's own decision in NotificationHelper::sendCardDuedate():
+	 *
+	 * - `off` never notifies — not even the owner of an unshared board;
+	 * - `all` always notifies;
+	 * - the owner of an unshared board is notified for every card, since on a
+	 *   board nobody else can see "assigned" would otherwise mean nothing;
+	 * - `assigned` notifies users assigned to the card, directly or through a
+	 *   group or circle.
+	 *
+	 * An unknown value is treated as Deck's default. Deck rejects anything
+	 * else when storing the setting, so that only happens if the preference
+	 * was edited by hand.
+	 *
+	 * @param bool|callable(): bool $isAssigned a callable is only invoked when
+	 *        the answer actually depends on it — it costs a query per user
+	 */
+	public static function shouldNotify(string $deckSetting, bool $isOwnerOfUnsharedBoard, bool|callable $isAssigned): bool {
+		if (!in_array($deckSetting, [self::DECK_OFF, self::DECK_ASSIGNED, self::DECK_ALL], true)) {
+			$deckSetting = self::DECK_DEFAULT;
+		}
+
+		if ($deckSetting === self::DECK_OFF) {
+			return false;
+		}
+		if ($deckSetting === self::DECK_ALL || $isOwnerOfUnsharedBoard) {
+			return true;
+		}
+
+		return is_callable($isAssigned) ? (bool)$isAssigned() : $isAssigned;
+	}
+}