add react-hot-toast and surface OpenAI API errors to users (#328)

pages/api/chat.ts

@@ -1,6 +1,6 @@
 import { ChatBody, Message } from '@/types/chat';
 import { DEFAULT_SYSTEM_PROMPT } from '@/utils/app/const';
-import { OpenAIStream } from '@/utils/server';
+import { OpenAIError, OpenAIStream } from '@/utils/server';
 import tiktokenModel from '@dqbd/tiktoken/encoders/cl100k_base.json';
 import { init, Tiktoken } from '@dqbd/tiktoken/lite/init';
 // @ts-expect-error
@@ -49,7 +49,11 @@ const handler = async (req: Request): Promise<Response> => {
     return new Response(stream);
   } catch (error) {
     console.error(error);
-    return new Response('Error', { status: 500 });
+    if (error instanceof OpenAIError) {
+      return new Response('Error', { status: 500, statusText: error.message });
+    } else {
+      return new Response('Error', { status: 500 });
+    }
   }
 };