Ruma can't currently handle an event with the wrong event content type.
When replacing the MessageEventStub's content it automatically
serializes as "m.room.redaction".
The MessageQueue holds MessageEventStub<AnyMessageEventContent> so when
a redaction event is encountered the redacted event's content can be
replaced. The Unsigned field redacted_because is also populated with the
redaction event itself with the addition of a room_id Stub -> full
event.
Also refactor and document why this hoisting is needed.
This change makes the user_presence test fail because the hoisting
exposes an error encoded into the test's expected result.
Previously, the test expected 2 members in the room at the end. This is
incorrect since one of the members in the test data leaves the room.
However, since the prev_content of state events was previously not
hoisted to the top level, the `membership_change` method would not
notice it and thus not realize the member had left the room. The test
was corrected to expect only a single member in the room.
Another test change was made due to a limitation of EventBuilder: due to
the fact that it makes the test data go through a de/ser cycle, it
cannot easily hoist prev_content to the top level. Because of this, the
tests were change to put prev_content into the top level from the
outset.
After discussing with poljar, we concluded we don't actually need to
tracking membership state, since we won't be tracking users that
left (banned, kicked, disinvited).
The only thing we need to keep track of is the difference between joined
and invited users which will be dealt with in a separate commit.
The client objects in the sdk accepted an optional session argument at
creation time. If provided this would restore the client into a logged
in state.
Since we need to restore the client state and encryption state at some
point it makes sense to do it when the client transitions into a logged
in state. At the same time we would like to avoid the client creation to
be async.
This introduces a restore_login() method which can be called instead of
the login() method to restore a session.
