FWIW I agree the solutions in that thread aren't good enough, especially since most of them are postgres specific. Now that migrations can be shipped with contr

FWIW I agree the solutions in that thread aren't good enough, especially since most of them are postgres specific. Now that migrations can be shipped with contrib.auth, a better solution might be possible. I'd probably prefer a functional unique index since it would be easier to maintain (rather than duplicate fields). We just need to get expression support into indexes.