Implement token authentication (Docker Registry HTTP API V2) #2442

The docker-java client does not yet support the token authentication flow defined by the official specification at https://distribution.github.io/distribution/spec/auth/token/

Authentication Flow (text):

1. Client sends initial request to registry without any authentication header.
2. Registry responds with 401 Unauthorized and a WWW-Authenticate header specifying the token endpoint.
3. Client issues a GET request to the token endpoint (/token) with service and scope query parameters.
4. Auth server returns JSON containing token, expires_in, and issued_at.
5. Client retries the registry request, including Authorization: Bearer .
6. Registry responds with 200 OK and the requested payload.

I would be willing to contribute this improvement with guidance from the docker-java community