Improve DocSum file handling

[eero-t]

Description

Use temporary file only when necessary, and use aiofiles own functionality for that.

Issues

n/a.

Type of change

• [x] Others (enhancement, documentation, validation, etc.)

Dependencies

n/a.

Tests

Just CI so far, so this is marked as draft.

[github-actions[bot]]

Dependency Review

✅ No vulnerabilities or license issues found.

Scanned Files

None

[eero-t]

Marking as draft, until also manually tested.

[eero-t]

@vrantala Rebased to main and fixed the conflicts => file read + b64encode() (for video/audio processing) is now also done with async/await.