code: public TaskConfigProperty addProperty(String propertyName) {
          TaskConfigProperty property = new TaskConfigProperty(propertyName);
          add(property);
          return property;
      }
docs: Adds a property to the configuration of this task.
  
  @param propertyName Name of the property (or key) in the configuration.
  
  @return an instance of {@link com.thoughtworks.go.plugin.api.task.TaskConfigProperty}