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>

src/stock_str.rs

@@ -423,6 +423,12 @@ https://delta.chat/donate"))]
 
     #[strum(props(fallback = "Incoming video call"))]
     IncomingVideoCall = 235,
+
+    #[strum(props(fallback = "You changed the chat description."))]
+    MsgYouChangedDescription = 240,
+
+    #[strum(props(fallback = "Chat description changed by %1$s."))]
+    MsgChatDescriptionChangedBy = 241,
 }
 
 impl StockMessage {
@@ -601,6 +607,19 @@ pub(crate) async fn msg_grp_img_changed(context: &Context, by_contact: ContactId
     }
 }
 
+pub(crate) async fn msg_chat_description_changed(
+    context: &Context,
+    by_contact: ContactId,
+) -> String {
+    if by_contact == ContactId::SELF {
+        translated(context, StockMessage::MsgYouChangedDescription).await
+    } else {
+        translated(context, StockMessage::MsgChatDescriptionChangedBy)
+            .await
+            .replace1(&by_contact.get_stock_name(context).await)
+    }
+}
+
 /// Stock string: `You added member %1$s.` or `Member %1$s added by %2$s.`.
 ///
 /// The `added_member_addr` parameter should be an email address and is looked up in the