update app.py to handle secret key

app.py

@@ -70,9 +70,15 @@ system_template = {
     "content": init_prompt,
 }
 
-# read key.key file and set openai api key
-with open("key.key", "r") as f:
-    key = f.read()
+# if file key.key exist read the key if note read the env variable OPENAI_TOKEN
+if os.path.isfile("key.key"):
+
+    # read key.key file and set openai api key
+    with open("key.key", "r") as f:
+        key = f.read()
+else:
+    key = os.environ["OPENAI_TOKEN"]
+
 
 # set api_key environment variable
 os.environ["api_key"] = key