Tie workflows to the board owner instead of their creator

A workflow now belongs to whoever owns its board. The settings page
lists, edits and deletes workflows by board ownership alone, using
Deck's BoardMapper::findAllByOwner(), a single owner query that never
returns shared boards and carries no frozen uid. A transferred board's
workflows therefore show up for the new owner immediately.

The background job still needs one user to run as and mail, so it
looks up the board owner before every run and stores it in user_id
when it changed. Archived boards stay listed so their workflows keep
a name, but are no longer offered or accepted as a target.

lib/Db/WorkflowMapper.php

@@ -22,24 +22,27 @@ class WorkflowMapper extends QBMapper {
 	 * @throws DoesNotExistException
 	 * @throws MultipleObjectsReturnedException
 	 */
-	public function findForUser(int $id, string $userId): Workflow {
+	public function findById(int $id): Workflow {
 		$qb = $this->db->getQueryBuilder();
 		$qb->select('*')
 			->from($this->getTableName())
-			->where($qb->expr()->eq('id', $qb->createNamedParameter($id, IQueryBuilder::PARAM_INT)))
-			->andWhere($qb->expr()->eq('user_id', $qb->createNamedParameter($userId)));
+			->where($qb->expr()->eq('id', $qb->createNamedParameter($id, IQueryBuilder::PARAM_INT)));
 
 		return $this->findEntity($qb);
 	}
 
 	/**
+	 * @param int[] $boardIds
 	 * @return Workflow[]
 	 */
-	public function findAllForUser(string $userId): array {
+	public function findAllForBoards(array $boardIds): array {
+		if ($boardIds === []) {
+			return [];
+		}
 		$qb = $this->db->getQueryBuilder();
 		$qb->select('*')
 			->from($this->getTableName())
-			->where($qb->expr()->eq('user_id', $qb->createNamedParameter($userId)))
+			->where($qb->expr()->in('board_id', $qb->createNamedParameter($boardIds, IQueryBuilder::PARAM_INT_ARRAY)))
 			->orderBy('id', 'ASC');
 
 		return $this->findEntities($qb);