code: public static void addCustomTagToProperties(Properties properties, Tag<?> tag) {
      // Build a state wrapper to add custom tag to property
      State state = new State(properties);
      addCustomTagToState(state, tag);
    }
docs: Add a {@link Tag} to a {@link Properties} with key {@link #METRICS_STATE_CUSTOM_TAGS}.
  Also see {@link #addCustomTagToState(State, Tag)}
  
  <p>
  The {@link Properties} passed can be used to build a {@link State}.
  {@link org.apache.gobblin.metrics.Tag}s under this key can later be parsed using the method {@link #getCustomTagsFromState}.
  </p>
  
  @param properties {@link Properties} to add the tag to.
  @param tag {@link Tag} to add.