Option to export colId as header in CSV / XSLX instead of label (#688)

[fflorent]

Context

Quoting @vviers in #688 :

We do a lot of downloading CSV from Grist in order to integrate data tables to a downstream data platform, and it's a little painful that the column names are human-friendly labels instead of the more machine-friendly colId.

This also defeats the purpose of disconnecting the column label from colId since any renaming of a column in a Grist doc breaks our ETL system if we forget / aren't told to update it as well (this would not happen if we relied on colId and disconnected them from labels*).

My idea is to add a new option to the download/csv endpoint (and to download/xlsx as well if you wish though I think less developers / automated systems would be impacted by this) in order to add the option of getting the file with colId instead of labels.

Solution

Add a ?colIdAsHeader=true|false ?header=colId option to both CSV and XLSX exports for that purpose.

resolves #688

[dsagal]

Given the wish in #690 to allow using persistent numeric IDs in the API (for tables, but could later be supported for columns too), might it make sense to have the option as headers=<label|colId> for the feature in this diff, and later add additional choices of skip and colRef (for numeric IDs)?

[fflorent]

@dsagal I hesitated with this option, and you have fair points in favor for this change!
Done :)

[georgegevoian]

Thanks @fflorent!