The "I left the group" message can't be sent to a protected group if some member's key is missing,
in this case we should remain in the group. The problem should be fixed first, then the user may
retry to leave the group.
There was a comment in `fetch_existing_msgs()`: "Bots don't want those messages". If a bot doesn't
want this setting, why enable it? It's disabled by default anyway.
`IsChatmail` is set also by `inbox_fetch_idle()`, but it isn't called during `configure()`. Setting
`IsChatmail` from `inbox_fetch_idle()` is necessary to handle client/server upgrades, but
`IsChatmail` also should be available for the app after configuring an account, e.g. DC Android
needs it to know whether to ask the user to disable battery optimisations.
Before this fix LogSink was dropped immediately,
resulting in no logs printed for contexts created using
TextContext::new_alice(), but printed for contexts created
using TextContext::new().
`!to_ids().is_empty()` check is needed in cases of 1:1 chat creation
because otherwise `to_id` is undefined,
but in case of outgoing group message without recipients
observed on a second device creating a group should be allowed.
When doing an AEAP transition, we mustn't just delete the old peerstate as this would break
encryption to it. This is critical for non-verified groups -- if we can't encrypt to the old
address, we can't securely remove it from the group (to add the new one instead).
async-broadcast returns Overflowed error once
if channel overflow happened.
Public APIs such as get_next_event JSON-RPC method
are only expecting an error if the channel is closed,
so we should not propagate overflow error outside.
In particular, Delta Chat Desktop
stop receiving events completely if an error
is returned once.
If overflow happens, we should ignore it
and try again until we get an event or an error because
the channel is closed (in case of recv())
or empty (in case of try_recv()).
If multiple headers with the same name are present,
we must take the last one.
This is the one that is DKIM-signed if
this header is DKIM-signed at all.
Ideally servers should prevent adding
more From, To and Cc headers by oversigning
them, but unfortunately it is not common
and OpenDKIM in its default configuration
does not oversign any headers.
