Normalise unicode for usernames

[Ryuno-Ki]

See #824 (comment)

Basically, follow the lead of Django (web framework, written in Python) when normalising the usernames for slugs.
This could please an international audience.

Unicode is hard, so use a lib (see linked comment).

[melvincarvalho]

Could you define username?

The characters used in the webid / subdomain should be alphanumeric with a dash, I think.

The nick and full names in the profile can be full unicode, and I think already are?

Unicode characters in URIs are a phishing vector. Responsible pod providers should avoid.

[akuckartz]

Unicode characters in URIs are a phishing vector.

Can you suggest any references?

[melvincarvalho]

Try a web search for homograph attack.

[Ryuno-Ki]

@melvincarvalho I learned, that the url is built like [username].[hostname].

@akuckartz I think, he's referring to typosquatting.

[Ryuno-Ki]

Ah, like in https://twitter.com/benbjohnson/status/533848879423578112 then