MarshalWithCustomFields marshals value merged with custom fields defined in the map into JSON bytes.

MergeCustomFields converts value to the JSON-like map and merges it with custom fields map cf.

ToMap convert object, string or bytes to json object represented by map.

ToMaps convert array to array of json objects.

UnmarshalWithCustomFields unmarshals JSON into value v and puts all JSON fields which do not belong to value into custom fields map cf.