feat(deposition): submit EMBL flatfile instead of fasta for better nucleotide metadata

[anna-parker]

resolves #

preview URL: https://test-adding-authors.loculus.org/

Summary

Adding AUTHORS as a field to the manifest file was not successful, from reading the docs it has become clear to us that instead of submitting the sequence as a fasta we should submit a flat file, flat files allow us to set metadata fields and the authors field.

Docs: https://ena-docs.readthedocs.io/en/latest/submit/fileprep/flat-file-example.html
Flat file: annotations: https://www.ebi.ac.uk/ena/WebFeat/.
As we are submitting as a broker it is important that we add the AUTHORS to the assembly: https://ena-docs.readthedocs.io/en/latest/faq/data_brokering.html#authorship.

Screenshot

PR Checklist

• All necessary documentation has been adapted.
• The implemented feature is covered by an appropriate test.