Prevent pdfalto subprocess call failing due input filename

[donaldgray]

Spaces + ampersands in PDF source url were seen to cause issues. PDF saved with safe name and source saved in txt file alongside for troubleshooting.

Resulting output will now be:

/works/{work-folder}/download.pdf
/works/{work-folder}/details.txt

details.txt isn't necessary and only added to aid debugging/troubleshooting as work-folder is randomly generated.

whereas previously it would be a single PDF, named using final part of URL

/works/{work-folder}/{last-part-of-url}

If the final path contained ' ' or & the subprocess call to /usr/bin/pdfalto would fail.

Unrelated to above fix but also bumped LocalStack image used for local testing.