Function serialize

src/serializers/RocksDbSerializer.cpp:34–50

@nb copied from IfcEntityInstanceData.cpp but operating on unresolved instances

namespace {
	// @nb copied from IfcEntityInstanceData.cpp but operating on unresolved instances
	bool serialize(std::string& val, const IfcParse::reference_or_simple_type& t)
	{
		auto s = sizeof(size_t);
		val.resize(s + 2);
		val[0] = TypeEncoder::encode_type<IfcUtil::IfcBaseClass*>();
		// 1 = entity - stored by id (entity name)
		// 2 = type - stored by identity (internal counter in class)
		val[1] = t.index() == 0 ? 'i' : 't';
		size_t iden;
		if (auto* name = std::get_if<IfcParse::InstanceReference>(&t)) {
			iden = *name;
		} else if (auto* inst = std::get_if<IfcUtil::IfcBaseClass*>(&t)) {
			iden = (*inst)->identity();
		}
		memcpy(val.data() + 2, &iden, s);
		return true;
	}

	bool serialize(std::string& val, const std::vector<IfcParse::reference_or_simple_type>& t)
	{