public static VersionedReference <TRef> UpdateIncrement <TAtomic, TRef>(
     this TAtomic atom,
     VersionedReference <TRef> newRefExpectedVersion)
     where TAtomic : IAtomic <VersionedReference <TRef> >
     where TRef : class;
 public bool Equals(VersionedReference <TRef> other)
 => ReferenceEquals(Reference, other.Reference) &&
 Version == other.Version;