Make sure that author is always assigned to imported posts

[vytisbulkevicius]

Description

When Feedzy is importing posts automatically author is not assigned and posts are created without an author:

This can cause issues in some cases like when permalinks are used with author in them.

We should store the user who created an import as author unless another author is selected, passed via URL:
https://docs.themeisle.com/article/942-in-feedzy-how-do-i#pass-author-ID

Or these options are enabled:

Step-by-step reproduction instructions

Create an import and run it - you will be the author of imported posts.
The next time cron runs and items are created automatically the author will be empty.

Screenshots, screen recording, code snippet or Help Scout ticket

No response

Environment info

No response

Is the issue you are reporting a regression

No