Support arbitrary fields for the acknowledgements download

[joverlee521]

Context

Original context in Slack thread.

Summary of the thread is we want to include segment accession in the acknowledgments table instead of the gisaid_epi_isl in the seasonal flu builds. This is currently not possible because the fields for the acknowledgments table is hard-coded in Auspice:

auspice/src/components/download/helperFunctions.js

Line 326 in 8e117aa

const traitsToExport = ["gisaid_epi_isl", "genbank_accession", "originating_lab", "submitting_lab"];

[jameshadfield]

From that slack thread there were two proposed solutions:

• add a field to the (dataset) JSON which defines what fields we want to export. Within workflows this would be defined in the auspice-config JSON and passed through augur export
• make auspice interpret accession_{X} as an accession, and thus export it