nor method
Combines this spec with another using NOR logic (NOT OR).
Returns a new spec that is satisfied only when neither this spec
nor other is satisfied — both must fail. Equivalent to calling
or followed by toNegated.
Prefer someSpec.or(other).toNegated() when readability matters.
Use nor as a convenience when the neither-nor intent is central
to the business rule.
Example:
// True only when the user is neither banned nor suspended
final fullyActive = IsBanned().nor(IsSuspended());
Implementation
Spec<T> nor(Spec<T> other) => _Nor(this, other);