class UserService  :4-17
  def __init__(db)
  def get_user(user_id)
  async def create_user(data)
class AdminService(UserService)  :20-22
  def delete_user(user_id)
def hash_password(password)  :25-27  # Returns deterministic hash for tests
async def send_email(to, subject, body)  :30-32  # Send transactional email to user inbox
