ingest: support Excel tables with new columns

[joverlee521]

Currently, the Excel tables are converted to NDJSON and concatenated to the existing cache. If an Excel table has a new columns, then the curate rule will fail because augur curate has a built-in validation to check all records have the same fields. I knew this could be an issue when initially setting up the ingest workflow, but I thought the GISAID metadata Excel table has been very stable over the last couple years and didn't add any guardrails. However, this came up when I was testing a new download that includes the new Publishing_Embargo_Until column.

TODOs

• check if concatenated NDJSONs have matching fields
• emit loud error to fix before cache gets uploaded
• add mechanism to rename/add fields to cache to match new Excel tables

[joverlee521]

For the embargo sequences, it's possible to completely exclude them from the download by checking exclude "TPE submissions".

[joverlee521]

This has become a higher priority issue since GISAID Excel tables no longer include the "Authors", "Originating_Lab", and "Submitting_Lab" columns.