Gets (and creates if necessary) an authentication token to be used for an external login parameter.
When a new token is created, it is persisted in the web session and in the web request and map entry keyed by the
token and valued by a userLogin object is added to a map that is looked up for subsequent requests.
request - - the http request in which the authentication token is searched and stored
the authentication token as persisted in the session and request objects
OFBiz controller event that performs the user authentication using the authentication token.
The method is designed to be used in a chain of controller preprocessor event: it always return "success"
even when the authentication token is missing or the authentication fails in order to move the processing to the
next event in the chain.