Useful filenames for downloads

## **Is your feature request related to a problem? Please describe.**
Hello, currently downloading media using voyager leads to unhelpful filenames like `Image_DATETIME_OFDOWNLOAD.jpg`.
Can you please change the filename format to be dependent on the posts title, author and post id?

As posts can fade away any time, this is a easy simple mobile-working way to archive locally. With a bit of source and description flavored filename it gets better traceable back. Also helps with every gallery/filemenager software to see what this is about without thumbnail.

Post / :

## **Describe the solution you'd like**
Something I use normally for such cases: Maximum 150/X characters. Post ID (or URL) and user id always. Rest for post title/description.
Example for water bottle post above:

* userid=`@Olap@lemmy.world` => `Olap-lemmy.world` 16c
* postid=`50568911` => `p50568911` 9c
* title=`New water bottle` (fill till length limit)
* description=`Old one’s thread has given up. Nicked a new one from work in white as it is almost identical. Didn’t want to unceremoniously ditch the old one, it did a great job for many years and saw many events, so here’s a post to celebrate it. Thank you old faithful, long live the new faithful!` (fill till length limit)
* File extension => `.jpg` ~4c

With slugified / non alphanumeric changed to hyphen, here are some example variations, depending on wanted filename length.

```
Olap-lemmy.world_p50568911_new-water-bottle-old-ones-thread-has-given-up-nicked-a-new-one-from-work-in-white-as-it-is-almost-identical-didnt-want-to.jpg

Olap-lemmy.world_p50568911_new-water-bottle-old-ones-thread-has.jpg

new-water-bottle_Olap-lemmy.world_p50568911_old-ones-thread-has-given-up.jpg

new-water-bottle_Olap-lemmy.world_p50568911_old-ones-thread-has-given-up-nicked-a-new-one-from-work-in-white-as-it-is-almost-identical-didnt-want-to.jpg
```

## **Describe alternatives you've considered**
For sure not how it's currently - no meaningful filenames.