Generalise to use FPE algorithms

[jayjun]

If I’m not mistaken, ScatterSwap is a form of format-preserving encryption.

A lot of work was done recently to have industry standards, with FF1 and FF3 submitted for review (and FF3 deemed unsuitable recently).

Surprisingly, I can only find one good open-source implementation and it’s written in Go (see capitalone/fpe).

It’s likely overkill for obfuscating IDs, but probably very useful in other scenarios.