auth: return early in LoginRequired on API key validation Simplify the logic in the LoginRequired decorator when Kallithea is accessed using an API key. Either: - the key is valid and API access is allowed for the accessed method (continue), or - the key is invalid (redirect to login page), or - the accessed method does not allow API access (403 Forbidden) In none of these cases does it make sense to continue checking for user authentication, so return early.