enum class parse_event_t : std::uint8_t { object_start, object_end, array_start, array_end, key, value };
The parser callback distinguishes the following events:
object_start: the parser read { and started to process a JSON objectkey: the parser read a key of a value in an objectobject_end: the parser read } and finished processing a JSON objectarray_start: the parser read [ and started to process a JSON arrayarray_end: the parser read ] and finished processing a JSON arrayvalue: the parser finished reading a JSON value