code: public <T extends Enum & Option> OptionsMapper props(final String prefix) {
          for (Object key : System.getProperties().keySet()) {
              final String name = (String) key;
              // don't look for directly mapped properties
              if (!mappedProps.contains(name) && name.startsWith(prefix)) {
                  final String optionName = name.substring(prefix.length());
                  final T option = OptionParser.recognizeOption(optionName);
                  register(PROP_PREFIX + name, option, System.getProperty(name), null);
              }
          }
          return this;
      }
docs: Search for system properties, prefixed with provided string. Property format must be:
  "(prefix)enumClassName.enumValue". For example: option.ru.vyarus.dropwizard.guice.GuiceyOptions.UseHkBridge
  where "option." is prefix.
  <p>
  Could be used only for string, boolean, integer, double, short and byte option types.
  <p>
  If some options require special handling then map them directly using {@link #prop(String, Enum, Function)}
  and only AFTER that call mass processing.
  
  @param prefix options prefix
  @param <T>    helper option type
  @return mapper instance for chained calls