docs: def marvcli_user_add(ctx, username, password):
      """Add a user"""
      if not re.match(r'[0-9a-zA-Z\-_\.@+]+$', username):
          click.echo('Invalid username: {}'.format(username), err=True)
          click.echo('Must only contain ASCII letters, numbers, dash, underscore and dot',
                     err=True)
          sys.exit(1)
      if password is None:
          password = click.prompt('Password', hide_input=True, confirmation_prompt=True)
      app = create_app()
      try:
          app.um.user_add(username, password, 'marv', '')
      except ValueError as e:
          click.echo('Error: {}'.format(e.args[0], err=True))
          sys.exit(1)