feat: Group and broadcast channel descriptions (#7829)

fix https://github.com/chatmail/core/issues/7766

Implementation notes:

- Descriptions are only sent with member additions, when the description
is changed, and when promoting a previously-unpromoted group, in order
not to waste bandwith.
- Descriptions are not loaded everytime a chat object is loaded, because
they are only needed for the profile. Instead, they are in their own
table, and can be loaded with their own JsonRPC call.

---------

Co-authored-by: iequidoo <117991069+iequidoo@users.noreply.github.com>

deltachat-repl/src/main.rs

@@ -179,7 +179,7 @@ const DB_COMMANDS: [&str; 11] = [
     "housekeeping",
 ];
 
-const CHAT_COMMANDS: [&str; 39] = [
+const CHAT_COMMANDS: [&str; 40] = [
     "listchats",
     "listarchived",
     "start-realtime",
@@ -192,6 +192,7 @@ const CHAT_COMMANDS: [&str; 39] = [
     "addmember",
     "removemember",
     "groupname",
+    "groupdescription",
     "groupimage",
     "chatinfo",
     "sendlocations",