Fix primary key usage with different types

Signed-off-by: Julius Härtl <jus@bitgrid.net>

lib/Db/User.php

@@ -24,11 +24,12 @@
 namespace OCA\Deck\Db;
 
 use OCP\IUser;
+use OCP\Share\IShare;
 
 class User extends RelationalObject {
 
 	public function __construct(IUser $user) {
-		$primaryKey = $user->getUID();
+		$primaryKey = IShare::TYPE_USER . ':' . $user->getUID();
 		parent::__construct($primaryKey, $user);
 	}
 
@@ -46,4 +47,4 @@ class User extends RelationalObject {
 	public function getDisplayName() {
 		return $this->object->getDisplayName();
 	}
-}
+}