input: Write a function to validate user data based on specific fields and values.
  assert validate_user({"body": {"name": "John Smith", "age": 29, "city": "New York"}}, None) == {"statusCode": 200, "body": "User has valid configuration"}
  assert validate_user({"body": {"name": "Jane Doe", "age": 29, "city": "New York"}}, None) == {"statusCode": 400, "body": "Invalid value for field name"}
  assert validate_user({"body": {"name": "John Smith", "age": 25, "city": "New York"}}, None) == {"statusCode": 400, "body": "Invalid value for field age"}
  assert validate_user({"body": {"name": "John Smith", "age": 29, "country": "USA"}}, None) == {"statusCode": 400, "body": "Invalid field country"}
output: def validate_user(event, context):
      valid_user = {"name": "John Smith", "age": 29, "city": "New York"}
      
      user_data = event.get("body", {})
      
      for field, value in user_data.items():
          if field not in valid_user:
              return {"statusCode": 400, "body": f"Invalid field {field}"}
          if user_data[field] != valid_user[field]:
              return {"statusCode": 400, "body": f"Invalid value for field {field}"}
      
      return {"statusCode": 200, "body": "User has valid configuration"}