'require_usage_rights' feature flag
'require_usage_rights' feature flag

test plan:
 - as site admin, set feature to 'allowed' in a root account
 - as a teacher in a course under this account, see that feature
   becomes available to be allowed in course settings

closes CNVS-15864

Change-Id: I569e6febf44bcf75a46bcbbbc25d15a99571cc46
Reviewed-on: https://gerrit.instructure.com/44567
Reviewed-by: Clay Diffrient <9dff2e5c98626d20d2848250c411e8009465bb87@instructure.com>
Tested-by: Jenkins <d95b56ce41a2e1ac4cecdd398defd7414407cc08@instructure.com>
QA-Review: Jahnavi Yetukuri <ed2b2672ccc2e59e56c0615df7f01b579202e014@instructure.com>
Product-Review: Cosme Salazar <d37f5e06cd46b8fd23ce5553334e09ede5394232@instructure.com>

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