Handling Non-ASCII usernames in the server

[teolemon]

What

• We recently spotted an issue related to logging with Non-ASCII usernames, which we solved in the Dart package
• Cannot login with a non-ASCII username openfoodfacts-dart#829
• This was a heads-up to server, and a question as to whether letting non-ascii usernames was desired, and whether it was properly handled in all situations.
• cc @monsieurtanuki @g123k

Part of

[hangy]

FWIW

openfoodfacts-server/lib/ProductOpener/Users.pm

Line 504 in 8d8be8e

elsif ($user_ref->{userid} !~ /^[a-z0-9]+[a-z0-9\-]*[a-z0-9]+$/) {

[alexgarel]

We prefer userid (aka user name) to be ascii for now (it becomes the filename, better stay safe).