code: public static Map<String, Object> toMapWithDefault(String value, Map<String, Object> defaultValue) {
  		Map<String, Object> result = toNullableMap(value);
  		return result != null ? result : defaultValue;
  	}
docs: Converts JSON string into map object or returns default value when conversion
  is not possible.
  
  @param value        the JSON string to convert.
  @param defaultValue the default value.
  @return Map object value or default when conversion is not supported.
  
  @see JsonConverter#toNullableMap(String)