🚑 fix(export): Issue exporting Conversation with Assistants (#2769)

* 🚑 fix(export): use content as text if content is present in the message

If the endpoint is assistants, the text of the message goes into content, not message.text.

* refactor(ExportModel): TypeScript, remove unused code

---------

Co-authored-by: Yuichi Ohneda <ohneda@gmail.com>

client/src/hooks/Messages/useBuildMessageTree.ts

@@ -0,0 +1,78 @@
+import { useRecoilCallback } from 'recoil';
+import type { TMessage } from 'librechat-data-provider';
+import store from '~/store';
+
+export default function useBuildMessageTree() {
+  const getSiblingIdx = useRecoilCallback(
+    ({ snapshot }) =>
+      async (messageId: string | null | undefined) =>
+        await snapshot.getPromise(store.messagesSiblingIdxFamily(messageId)),
+    [],
+  );
+
+  // return an object or an array based on branches and recursive option
+  // messageId is used to get siblindIdx from recoil snapshot
+  const buildMessageTree = async ({
+    messageId,
+    message,
+    messages,
+    branches = false,
+    recursive = false,
+  }: {
+    messageId: string | null | undefined;
+    message: TMessage | null;
+    messages: TMessage[] | null;
+    branches?: boolean;
+    recursive?: boolean;
+  }): Promise<TMessage | TMessage[]> => {
+    let children: TMessage[] = [];
+    if (messages?.length) {
+      if (branches) {
+        for (const message of messages) {
+          children.push(
+            (await buildMessageTree({
+              messageId: message?.messageId,
+              message: message,
+              messages: message?.children || [],
+              branches,
+              recursive,
+            })) as TMessage,
+          );
+        }
+      } else {
+        let message = messages[0];
+        if (messages?.length > 1) {
+          const siblingIdx = await getSiblingIdx(messageId);
+          message = messages[messages.length - siblingIdx - 1];
+        }
+
+        children = [
+          (await buildMessageTree({
+            messageId: message?.messageId,
+            message: message,
+            messages: message?.children || [],
+            branches,
+            recursive,
+          })) as TMessage,
+        ];
+      }
+    }
+
+    if (recursive && message) {
+      return { ...message, children: children };
+    } else {
+      let ret: TMessage[] = [];
+      if (message) {
+        const _message = { ...message };
+        delete _message.children;
+        ret = [_message];
+      }
+      for (const child of children) {
+        ret = ret.concat(child);
+      }
+      return ret;
+    }
+  };
+
+  return buildMessageTree;
+}