Remove temporary spawn message to fix notifications

[aldehir]

The temporary !spawn_message <id> message prevents users from getting notifications when edited to include their handle. This removes that temporary message and posts the ready list.

A change to the send queue mechanism was required to include a callback, this way we can grab the message reference without relying on reading it from the on message event.

[dcramps]

lgtm

[dcramps]

is **kwargs the pythonic way of doing variadics?

[aldehir]

@dcramps Yeah, kind of. When used as arguments to a function,*args and/or **kwargs, it'll unpack args for positional arguments and kwargs for the keyword arguments, respectively.

Variadics in python can be done like this.

def print_args(*args, **kwargs):
    print(args)
    print(kwargs)

>>> print_args(1, 2, 3, a=4, b=5)
(1, 2, 3)
{"a": 4, "b": 5}

As arguments,

def print_name(first, last, middle=None):
    return f"{first} {middle} {last}"

>>> name = ("john", "doe")
>>> opts = {"middle": "smith"}
>>> print_name(*name, **opts)
john smith doe

See iterable unpacking and dictionary unpacking.