Generate rfc724_mid when creating Message (#6704)

Set `rfc724_mid` in `Message::new()`, `Message::new_text()`, and
`Message::default()` instead of when sending the message. This way the
rfc724 mid can be read in the draft stage which makes it more consistent
for bots. Tests had to be adjusted to create multiple messages to get
unique mid, otherwise core would not send the messages out.

deltachat-ffi/src/lib.rs

@@ -37,6 +37,7 @@ use deltachat::*;
 use deltachat::{accounts::Accounts, log::LogExt};
 use deltachat_jsonrpc::api::CommandApi;
 use deltachat_jsonrpc::yerpc::{OutReceiver, RpcClient, RpcSession};
+use message::Viewtype;
 use num_traits::{FromPrimitive, ToPrimitive};
 use rand::Rng;
 use tokio::runtime::Runtime;
@@ -2076,7 +2077,7 @@ pub unsafe extern "C" fn dc_get_msg(context: *mut dc_context_t, msg_id: u32) ->
                         ctx,
                         "dc_get_msg called with special msg_id={msg_id}, returning empty msg"
                     );
-                    message::Message::default()
+                    message::Message::new(Viewtype::default())
                 } else {
                     warn!(ctx, "dc_get_msg could not retrieve msg_id {msg_id}: {e:#}");
                     return ptr::null_mut();