[MLS] Comments on Leaf Operation Intents

[Rohan Mahy <[e-mail]>]

Hi,
First, this document was easy to understand.

While addressing the problem of clients having to manage state for their
own removal, this seems to just sweeps under the rug the problem that under
some circumstances†, a client could have valid keying information for
several future epochs after another of its clients sent an intent for all
the user's clients to leave. Why not just make external committers get all
pending proposals and be done with it? That would assure deletion during
the next epoch transition. Is there a benefit I am overlooking?

Next, I think we are overusing WireFormats. I think if we implement
intents, we really want a new content type that reuses PrivateMessage,
SemiPrivateMessage, or PublicMessage, but has an `intents` ContentType
which shares the handshake ratchet with commit and proposal.

Thanks,
-rohan

†in the face of a bunch of external commits coming quickly (ex: a burst of
join activity)