add setting for oath token request timeout

fixes CNVS-13010

test plan
 - request an oauth token
 - it should not be valid after 10 min by default
 - it should allow changing the value as a setting

Change-Id: I2fd0457ab8a2e0e16729ce6b5fc854e1f834640b
Reviewed-on: https://gerrit.instructure.com/35713
Reviewed-by: Cody Cutrer <cody@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
Product-Review: Rob Orton <rob@instructure.com>
QA-Review: Rob Orton <rob@instructure.com>