use file2 zstd wrapper to read frag data (untested)

src/fragment_store/uuid_generator.hpp

@@ -9,6 +9,7 @@ struct UUIDGeneratorI {
 	virtual std::vector<uint8_t> operator()(void) = 0;
 };
 
+// TODO: templates?
 struct UUIDGenerator_128_128 final : public UUIDGeneratorI {
 	private:
 		std::array<uint8_t, 16> _uuid_namespace;