Rename patrons, add library cards

Rename some patrons to avoid everyone being John Q Public, add
mapping from library cards to users.

Signed-off-by: Jeff Godin <jgodin@tadl.org>
Auth by barcode, return user id, handle not-found

Use barcodes (and any password) to auth users, reutrn a user id in
the auth data, and return 404 when a user is not found.

Signed-off-by: Jeff Godin <jgodin@tadl.org>