code: public static Constraint truthy() {
  		return new Constraint("true", simplePayload("true")) {
  			public boolean isValid(Object actualValue) {
  				if (actualValue != null) {
  					if ((actualValue instanceof Boolean && !((Boolean) actualValue))
  							|| (actualValue instanceof String && !Boolean.parseBoolean((String) actualValue))) {
  						return false;
  					}
  				}
  				return true;
  			}
  		};
  	}
docs: The 'truthy' constraint - field value must be equal to 'true'.
  @return constraint