tiddlywebplugins.magicuser is a tool to extend the capabilities
of a user in TiddlyWeb.

When an authentic user is extracted from the credentials extractor
system, the username and their roles are places into the WSGI
environment as the value of a tiddlyweb.usersign key.

magicuser extends these capabilities by providing a model
for adding additional keys and values to the tiddlyweb.usersign
dictionary.

It does this by looking in a bag, by default called MAGICUSER,
for a tiddler with the same title as the value of the name key
in the usersign dict. If that tiddler is present, it is loaded
and it's attributes and fields are used (as shown in the code)
to add to the usersign.

BEFORE the magicuser bag is inspected, a username translation
layer is engaged. This allow N different authenticated usersigns
to be treated as one core usersign within TiddlyWeb. It works as 
follows:

A tiddler with a title that is the same as the extracted usersign
name is retrieved from a bag by default called MAPUSER. If the
tiddler exists and has the field mapped_user the value of the 
field replaces the name in the usersign. It is that name that
is then used during the magicuser stage.

This plugin provides no facility for putting tiddlers in either
the MAGICUSER or MAPUSER bags. Other code (either client side
or server side) is expected to do that.