add direct GET param to invite email 'view share' link to make sure g…

…uests can login when SSO is enabled (with user_saml, user_oidc...)

Signed-off-by: Julien Veyssier <julien-nc@posteo.net>

lib/Mail.php

@@ -110,7 +110,7 @@ public function sendGuestInviteMail(string $uid, string $shareWith, Share\IShare
 		$expiration = $share->getExpirationDate();
 
 		$link = $this->urlGenerator->linkToRouteAbsolute(
-			'files.viewcontroller.showFile', ['fileid' => $share->getNodeId()]
+			'files.viewcontroller.showFile', ['fileid' => $share->getNodeId(), 'direct' => 1]
 		);
 
 		$emailTemplate = $this->mailer->createEMailTemplate('guest.invite');