input: Write a python function to identify the number of days until a given date.
  assert days_until("12/25/2022") >= 0
  assert days_until("01/01/2023") >= 0
  assert days_until("07/04/2023") >= 0
output: def days_until(date_str):
      from datetime import datetime
      
      target_date = datetime.strptime(date_str, "%m/%d/%Y")
      current_date = datetime.now()
      
      delta = target_date - current_date
      return delta.days