add more indexes to support foreign keys

Change-Id: I4011daaf5b12ef47ed01d502eef401dabff7f927
Reviewed-on: https://gerrit.instructure.com/35297
Reviewed-by: Jacob Fugal <jacob@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>