Comment 4 for bug 1680062

It looks to me like this is set on a per-project basis. oslo.middleware doesn't have any default headers: https://github.com/openstack/oslo.middleware/blob/2c557312519cd368c50eaaa5448049da19cc6281/oslo_middleware/cors.py#L50

A quick search suggests that the accepted headers are being set in Glance itself: https://github.com/openstack/glance/blob/8a2d1542348e8aaaee163ba629fd37c534d469d9/glance/common/config.py#L851 I think that's where this would need to be changed.