auth_systems is a configuration setting that controls which
challengers are available to this
TiddlyWeb instance. It is a list of strings with each string representing the name of a module that implements the
ChallengerInterface. The name is first looked up in the
tiddlyweb.web.challengers package space. If not found there,
sys.path is searched.
If there is only one
challenger configured a request that redirects to the challenger system will go directly to that challenger. If there are multiple challengers configured the user will be presented with a list of choices.