Make sure OpenFileInAppProvider in OCM shares gets correct username

[glpatcern]

So this is not forgotten as a remaining issue from #1140.

Comment from @ishank011: can't do that with the current implementation. We're passing the same token around as the original user and can't make changes to it as we don't know the jwt secret of the other site. This won't be an issue in the public shares implementation so I think we can leave it be.
#1140 (comment)_

Not sure I understand why public shares won't be affected - in public shares, username essentially is "anonymous". Conversely, one of the key advantages of federated (OCM) shares is the ability to support federated identities.

[glpatcern]

This was fixed as part of the large refactoring around the OCM implementation