use conditional imports and show help errors if modules not found

src/dailyai/services/whisper_ai_services.py

@@ -3,10 +3,18 @@ import asyncio
 from enum import Enum
 import logging
 from typing import BinaryIO
-from faster_whisper import WhisperModel
 from dailyai.services.local_stt_service import LocalSTTService
 
 
+try:
+    from faster_whisper import WhisperModel
+except ModuleNotFoundError as e:
+    print(f"Exception: {e}")
+    print(
+        "In order to use Whisper, you need to `pip install dailyai[whisper]`.")
+    raise Exception(f"Missing module: {e}")
+
+
 class Model(Enum):
     """Class of basic Whisper model selection options"""
     TINY = "tiny"