Auth management for long running jobs

[soxofaan]

When aggregator is managing a "large" job (e.g. split across multiple backends) it has to be able to act on behalf of the user "in the background" (outside of the context of a user API request).
Necessary access tokens might not be available or expire too quickly.

Possible solutions:

• User also shares refresh token in addition to access token. This doesn't seem to fall in "best practices" category security-wise at first sight.
• A new mechanism for longer term machine-to-machine authentication (e.g. someting like API tokens or SSH pubkey auth)
• ...?