Refactor authentication handling in app.py and update Bedrock client configuration to use environment variables for provider

app.py

@@ -5,7 +5,7 @@ from langchain.schema import SystemMessage, HumanMessage, AIMessage
 import os
 
 
-AUTHS = os.environ.get('USERS')
+AUTHS = [(os.environ.get('USER'), os.environ.get('PW'))]
 
 def chat(message, history):
     # 3a) Build Bedrock input (with system prompt + raw dict‐history)

bedrock_client.py

@@ -19,7 +19,7 @@ bedrock_llm = ChatBedrockConverse(
     aws_access_key_id       =os.environ.get("AWS_ACCESS_KEY_ID"),
     aws_secret_access_key   =os.environ.get("AWS_SECRET_ACCESS_KEY"),
     region_name             =os.environ.get("AWS_DEFAULT_REGION", "eu-west-1"),
-    provider                = "mistral",
+    provider                = os.environ.get("PROVIDER", "mistral"),
     model_id                =os.environ.get("MODEL_ID", "mistral.mistral-large-2402-v1:0"),  # or your preferred Bedrock model
     temperature= 0.7)