import translations author is anonymous

Problem/Motivation

When importing content (at least from a single YAML file), the author of the translations is not properly imported.
However, when looking in the YAML file, the author is properly set.

Steps to reproduce

1. Export a content with its translation using drush (single YAML file)
2. Import the exported content using drush

Proposed resolution

Remaining tasks

User interface changes

API changes

Data model changes