319|Bugfix: user_login default set as current session's user, got from system information.

Description of fix

Added default attribute for user_preferences.user_login as current session's user to always have an author for a Note.

How to test it

1. Be sure your cfg.json has no user_login parameter.
2. Load a timeline.
3. Create new comment.
4. Publish
5. Link the review, the note has an author.

Checklist

Please check if your MR fulfills the following requirements:

• Build was run locally and any changes were pushed
• Lint has passed locally without error
• CHANGELOG.md has been updated
• Branch has been rebased on merge branch

FYI: @awesome_dev_too