Method on_document_begin

test/test.hpp:158–158

        constexpr static std::size_t max_string_size = std::size_t(-1);

        bool on_document_begin( system::error_code& ) { return true; }
        bool on_document_end( system::error_code& ) { return true; }
        bool on_object_begin( system::error_code& ) { return true; }
        bool on_object_end( std::size_t, system::error_code& ) { return true; }