Create two additional "context" based LTI middleware classes that perform the actual storage and retrieval of the lti launch params.  The LTIAuthMiddleware class now just sets the new set of launch params directly on the request during a launch, in addition to doing the actual authentication.  Users of the LTI auth library can choose whether to use single context or multiple (or neither) by adding either of the two context middleware classes to the list of installed middleware.