multi user: canonical username

[oliver-sanders]

On some systems, it might be possible for a user to authenticate using multiple different user names.

This is fine, however, for multi-user setups it may make it hard for users to access other users servers because the user name you authenticate with is what Jupyter Hub configures the configurable-http-proxy to use for accessing your server.

E.G. If a user can authenticate as either:

• usera
• usera.some.domain

Then the URL to their server would be either:

• https://hub-url/users/usera/
• https://hub-url/users/usera.some.domain/

For these setups it would be advantageous to have a canonical user name to avoid the confusion.

Ideas:

• Scan Jupyter docs, if we're lucky there may be a configuration somewhere?
• Subclass the authenticator?
• Pre-populate user records in the DB?