fix: add cache to forum role lookup
fix: add cache to forum role lookup

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