bug: error when importing podcast with escaped characters in files url
### Describe the bug
When a podcast to import has escaped characters in files url to import, error 404 is raised.
### Steps to reproduce
1. Go to import a podcast
2. Select a podcast from Anchor (eg. https://anchor.fm/s/4dc1d304/podcast/rss )
3. Launch import
4. See the error
### Expected behavior
Podcast should be imported.
### Actual behavior
Podcast is not imported.
### Relevant logs and/or screenshots
Import is trying to import
`https://anchor.fm/s/4dc1d304/podcast/play/27458623/https:/d3ctxlq1ktw2nl.cloudfront.net/staging/2021-1-26/b0514a0e-a5a0-4ccd-d558-6b50cb7ea15a.mp3`
instead of
`https://anchor.fm/s/4dc1d304/podcast/play/27458623/https%3A%2F%2Fd3ctxlq1ktw2nl.cloudfront.net%2Fstaging%2F2021-1-26%2Fb0514a0e-a5a0-4ccd-d558-6b50cb7ea15a.mp3`
### Context
- Castopod: alpha-45
- OS: Ubuntu
- Browser: Any
- Web server: Any
### Possible fixes
media_helper `download_file($file_url)` is using `\CodeIgniter\HTTP\URI` which messes everything up with URLs.
Do not use `\CodeIgniter\HTTP\URI` as `\Config\Services::curlrequest()->get()` want a string parameter anyway…
issue