HandlerRegistry.add_handler method ignores tuples in authenticators parameter

[martinHrabina]

Hello everybody,

due to changes earlier this year, method add_handler of class HandlerRegistry silently ignores parameter authenticators if Tuple[Authenticator] is provided, resulting in authenticators being []. This is an issue especially when the value for this field comes from default value of another method, since lists (as mutable types) are discouraged and tuples are preferred in default values.

I'd expect either an error raised when unexpected type is received, and/or preferably to accept also tuples or iterables in general.