## Issue Addressed
`Epoch::end_slot()` returns incorrect value when the epoch is the last epoch which can be represented by u64.
```rust
let slots_per_epoch = 32;
// The last epoch which can be represented by u64.
let epoch = Epoch::new(u64::max_value() / slots_per_epoch);
println!("{}", epoch.end_slot(slots_per_epoch));
// Slot(18446744073709551614)
// -> correctly, the result should be `Slot(18446744073709551615)`.
```
3d07934ca0