code: static Map<String, Object> digitsPayload(final Object i, final Object f) {
  		if (i == null || f == null) {
  			return null;
  		}
  		Map<String, Object> payload = new LinkedHashMap<>();
  		payload.put("integer", i);
  		payload.put("fraction", f);
  		payload.put("message", MSG_PREFIX + VALIDATORS.get(Digits.class));
  		return payload;
  	}
docs: Creates a new map representing a {@link Digits} validation constraint.
  @param i the max size of the integral part of the number
  @param f the max size of the fractional part of the number
  @return a map