fix: Mark user change as expected in LTIToolLaunchView.post
fix: Mark user change as expected in LTIToolLaunchView.post

The lti user gets authenticated and logged in as a part of the LTI View
Post.  This results in the request user changing during the request.  We
mark it here so that it does not produce a false alarm in our
SafeSessions middleware.

eduNEXT/edx-platform,angelapper/edx-platform,eduNEXT/edx-platform,arbrandes/edx-platform,edx/edx-platform,edx/edx-platform,angelapper/edx-platform,arbrandes/edx-platform,arbrandes/edx-platform,eduNEXT/edx-platform,edx/edx-platform,edx/edx-platform,angelapper/edx-platform,eduNEXT/edx-platform,arbrandes/edx-platform,angelapper/edx-platform