code: public static BooleanCliParam optional(Identifier identifier, boolean defaultValue, boolean nullable) {
          return new BooleanCliParam(identifier, Opt.of(MoreSuppliers.of(defaultValue)), nullable);
      }
docs: Construct an optional CLI boolean parameter with the given default value.
  
  @param identifier Parameter identifier.
  @param defaultValue Default value to be used by the parameter if it isn't explicitly bound.
  @param nullable Whether the parameter is nullable.
  @return A CLI boolean parameter constructed from the given parameters.