Such a message may be assigned to a wrong chat (e.g. undecipherable group msgs often get assigned to
the 1:1 chat with the sender). Add `DownloadState::Undecipherable` so that messages referencing
undecipherable ones don't go to that wrong chat too. Also do not reply to not fully downloaded
messages. Before `Message.error` was checked for that purpose, but a message can be error for many
reasons.
Message.set_text() and Message.get_text() are modified accordingly
to accept String and return String.
Messages which previously contained None text
are now represented as messages with empty text.
Use Message.set_text("".to_string())
instead of Message.set_text(None).
This further reduces the cognitive overload of having many ways to do
something. The same is very easily done using composition. Followup
from 82ace72527.
This also removes BackupProvider::join in favour of implementing
Future directly. I wondered about implementing a FusedFutre to make
this a little safer but it would introduce a dependency on the futures
crate in deltachat-ffi which did not exist yet, so I didn't do that.
get_chat_msgs() function is split into new get_chat_msgs() without flags
and get_chat_msgs_ex() which accepts booleans instead of bitflags.
FFI call dc_get_chat_msgs() is still using bitflags for compatibility.
JSON-RPC calls get_message_ids() and get_message_list_items()
accept booleans instead of bitflags now.
