- instrument snapshot creation to assure we see errors (which are ignored in code)
- move tests for public `entry` types into integration tests
- rename `OperationType` to `OperationKind` as it's more commmon in Rust
- Use `Copy` where possible
- streamline implementation: remove clones and allocations, without going zero-copy
- Prefer direct calls to traits to avoid `write!("{}")` just to invoke a trait fmt implementation
- avoid `pub` when `pub(crate)` will do
- strong type for created_at
