Gracefully fail when unable to access a mailbox

Expected behavior

If the apps/mail/api/mailboxes?accountId={accountId} endpoint is unable to access a mailbox for whatever reason, the fail should be handled gracefully and the user should be notified.

Actual behavior

The exception is thrown in MailboxSync::sync but isn't handled in MailManager but instead ignored.

To do

• Handle the exception upwards to the controller
• Add a JSONResponse::fail with the correct response data
• Add an indication to the frontend that notifies the user of an issue with this account

In lib/Service/MailManager.php

	/**
	 * @param Account $account
	 *
	 * @return Mailbox[]
	 * @throws ServiceException
	 */
	public function getMailboxes(Account $account): array {
		try {
			$this->mailboxSync->sync($account, $this->logger);
		} catch( ServiceException $e) {
			throw $e;
		}

		return $this->mailboxMapper->findAll($account);
	}

Some code from debugging this a bit:

In lib/Controller/MailboxesController.php

	/**
	 * @NoAdminRequired
	 * @TrapError
	 *
	 * @param int $accountId
	 *
	 * @return JSONResponse
	 *
	 * @throws ClientException
	 * @throws ServiceException
	 */
	public function index(int $accountId): JSONResponse {
		$account = $this->accountService->find($this->currentUserId, $accountId);
		try {
			$mailboxes = $this->mailManager->getMailboxes($account);
		} catch(ServiceException $e) {
			return HttpJsonResponse::fail(['Could not access mailbox for account ' . $account->getEMailAddress()]);
		}

		return new JSONResponse([
			'id' => $accountId,
			'email' => $account->getEmail(),
			'mailboxes' => $mailboxes,
			'delimiter' => reset($mailboxes)->getDelimiter(),
		]);
	}

src/components/Dashboard.vue needs to handle this error as well as the mail app.

Start with lib/Service/MailManager.php and lib/Controller/MailboxesController.php for the apps/mail/api/mailboxes?accountId={accountId} flow, then inspect src/components/Dashboard.vue. Trace the ServiceException from MailboxSync::sync and determine the expected failure response and frontend notification behavior. Done means the exception reaches the controller, the endpoint returns the appropriate JSON failure, and both the dashboard and mail app notify the user.