Add bearer authz to curl-backed files

[jblomer]

Feature description

The TCurlConnection should be able to attach a bearer authorization token. Interesting points are

• Testing
• Implementing SciToken discovery protocol (e.g. https://cds.cern.ch/record/2813819/files/document.pdf (Section 3))
• Interface in TFile, RRawFile to manually set tokens (see https://root-forum.cern.ch/t/using-root-with-eos-files-with-macaroons/64945/4)

Alternatives considered

No response

Additional context

No response