graphql: convert group type to class api
graphql: convert group type to class api

Test plan: specs pass

Change-Id: I5774a1e65d819a559ba22ee689b8d8c85159f775
Reviewed-on: https://gerrit.instructure.com/163100
Reviewed-by: Jonathan Featherstone <c99460343437e667b0585ea68fd7caf7bd0a02ab@instructure.com>
Tested-by: Jenkins
Product-Review: Cameron Matheson <1d572acbfa68c7c6e541c7b840d6b622e5c0dc91@instructure.com>
QA-Review: Cameron Matheson <1d572acbfa68c7c6e541c7b840d6b622e5c0dc91@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,djbender/canvas-lms,djbender/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,instructure/canvas-lms,instructure/canvas-lms,sfu/canvas-lms,sfu/canvas-lms