Write new class definitions

I need a new class to represent an in-game inventory item that can be stacked, serialized to save files, and compared for sorting. It must expose a public constructor taking an ID string, quantity int, and a timestamp, provide methods to increase and decrease quantity with bounds checks, return a compact binary serialization for disk, and implement operator< for stable sorting by rarity then timestamp. Write the class definition and method signatures in header-style, including const correctness and noexcept where appropriate.

Before I add this inventory class to the codebase, make it easy for other engineers to review and use. Surface the invariants up front: max stack size, valid ID format, and ownership semantics. Make method names self-explanatory, group serialization and mutation methods, and flag any places a reviewer will hesitate: implicit conversions, throwing constructors, or non-atomic quantity updates.

I just pushed a constructor that throws on empty ID; I expect callers will sometimes pass legacy data and I’m afraid this will crash save-load paths in debugging. Tell me the likely problem, whether to switch to a non-throwing repair path or keep the throw and update callers, and give the safest next code change to make now with minimal churn.

Every time I add a new item type I duplicate a class and tweak three fields. It costs review time and breaks serialization compatibility. Where am I losing time and credibility, and what two habits should I change to prevent this pattern — one technical (design a stable base class or variant) and one procedural (how to gate additions at code review)?