docker client: fix requests made against bearer token services
docker client: fix requests made against bearer token services

Previous to this commit the requests made against a bearer token service
would be lacking the `author` field.
That causes the jwt token to have an empty `sub` (Subject) field. [1]

The docker registry relies on the `sub` field to know the author of all
the requests. When a registry is configured to send notifications [2]
the resulting webhooks calls will be missing the author too.

This commit fixes the issue by reproducing the same request made by
the docker client.

[1] https://docs.docker.com/registry/spec/auth/jwt/#getting-a-bearer-token
[2] https://docs.docker.com/registry/configuration/#notifications

Signed-off-by: Flavio Castelli <d1035a58d87d0b7918844ad2fd699273faf2f5d5@suse.com>

containers/image,containers/image