Modify authorization_checks.cpp within getPrivilegesForAggregate to check each LiteParsedDocumentSource. If requiresAuthChecks() is true for a stage but its requiredPrivileges() returns an empty vector, return a Status(ErrorCodes::MissingAuthCheck).

Make sure to encapsulate this check with the feature flag created. That is to say, only the check should happen when the gFeatureFlagMandatoryAuthChecks featureflag is on.