settings: Fix re-ordering folders when there is an archived folder.

This commit updates webapp code to include archived folder IDs as
well in the "order" list passed when re-ordering folders.

Also, updated API documentation to mention that archived folder IDs
should also be included.

web/src/settings_folders.ts

@@ -22,6 +22,13 @@ function update_folder_order(this: HTMLElement): void {
     $(".channel-folder-row").each(function () {
         order.push(Number.parseInt($(this).attr("data-channel-folder-id")!, 10));
     });
+    const archived_folders = channel_folders
+        .get_channel_folders(true)
+        .filter((folder) => folder.is_archived)
+        .sort((a, b) => util.strcmp(a.name.toLowerCase(), b.name.toLowerCase()));
+    for (const folder of archived_folders) {
+        order.push(folder.id);
+    }
     settings_ui.do_settings_change(
         channel.patch,
         "/json/channel_folders",

zerver/openapi/zulip.yaml

@@ -24554,6 +24554,10 @@ paths:
                   type: array
                   description: |
                     A list of channel folder IDs representing the new order.
+
+                    This list must include the IDs of all the
+                    organization's channel folders, including archived
+                    folders.
                   items:
                     type: integer
             encoding: