feat: add api endpoint and UI to transfer a board to a different user

Signed-off-by: Luka Trovic <luka@nextcloud.com>

lib/Controller/BoardController.php

@@ -155,4 +155,15 @@ class BoardController extends ApiController {
 	public function clone($boardId) {
 		return $this->boardService->clone($boardId, $this->userId);
 	}
+
+	/**
+	 * @NoAdminRequired
+	 * @param $boardId
+	 * @param $owner
+	 * @param $newOwner
+	 * * @return null|void
+	 */
+	public function transferOwner($boardId, $owner, $newOwner) {
+		return $this->boardService->transferOwnership($owner, $newOwner);
+	}
 }

lib/Service/BoardService.php

@@ -746,6 +746,12 @@ class BoardService {
 		$this->boardsCache = null;
 	}
 
+	private function getBoardOwner($boardId) {
+		$board = $this->boardMapper->find($boardId);
+
+		return $board->getOwner();
+	}
+
 	/**
 	 * Clean a given board data from the Cache
 	 */