refs INTEROP-6890
TEST PLAN:
1) insert base64 encoded keypairs to the
inst_access_signing config file
2) start your server
3) it does not explode
Change-Id: I286bf1e335d7ceb95df4f847f9e96231ba1336bf
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/270905
Reviewed-by: Michael Ziwisky <mziwisky@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Ethan Vizitei <evizitei@instructure.com>
Product-Review: Ethan Vizitei <evizitei@instructure.com>