As a tarchive uploader
I want to create an uncorrupted tar file when I upload files via the API
So that the tarchive contents can be safely downloaded

Given tarchive_service.rs is responsible for creating tarchives via create_tarchive function
When adding an index (created through Tarchive::index) to the new archive
Then create a fresh second tar file and include the index, rather than appending the index to the first tar file, to avoid the tar append bug

Given tarchive_service.rs is responsible for updating tarchives via update_tarchive function
When adding files and/or an index (created through Tarchive::index) to an existing archive
Then create a fresh second tar file, extract and add files from the existing tar and the index, rather than appending the files to the first tar file, to avoid the tar append bug

Implementation Notes

- Place any unit tests at the bottom of the same file as the associated production code
- Increment patch version of anttp package in Cargo.toml
- Create a copy of this issue description and save to /spec using the name of this issue as the filename (with lower underscore case, starting with the 5 char padded issue number, e.g. 00001_issue_title.txt)
- There is a bug in the tar crate that corrupts tar files when appending to them after they have been saved. Re-creating the tar files from scratch should avoid this bug
