fix: Add self-addition message to chat when recreating member list

A user reported to me that after they left a group, they were implicitly readded, but there's no any
readdition message, so currently it looks in the chat like leaving it has no effect, just new
messages continue to arrive. The readdition probably happened because some member didn't receive the
user's self-removal message, anyway, at least there must be a message that the user is readded, even
if it isn't known by whom.

src/receive_imf.rs

@@ -2333,6 +2333,19 @@ async fn apply_group_changes(
                 context,
                 "Recreating chat {chat_id} member list with {new_members:?}.",
             );
+            if !self_added
+                && (chat.blocked == Blocked::Request || !chat_contacts.contains(&ContactId::SELF))
+            {
+                warn!(context, "Implicit addition of SELF to chat {chat_id}.");
+                group_changes_msgs.push(
+                    stock_str::msg_add_member_local(
+                        context,
+                        &context.get_primary_self_addr().await?,
+                        ContactId::UNDEFINED,
+                    )
+                    .await,
+                );
+            }
         }
 
         if new_members != chat_contacts {