add foreign key index part 5

Change-Id: If8e99a709499a1b0d100a2d87b1766392e0272d6
Reviewed-on: https://gerrit.instructure.com/45268
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Simon Williams <simon@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>