Google Sheets publish link no longer works due to redirect with broken CORS

[alexjball]

The request to sheets redirects with a 307 to what looks like a cache server. That server responds with the spreadsheet content but does not set the access-control-allow-origin header, which fails the request due to CORS. This is a server side issue that we can't fix on the client. Downloading directly still works

Immediate-term we can include the csv in the site so the page loads, but we won't pull in new providers.

Long term options:

1. We can use the Google Drive API to download the sheet. This may require authenticating as a user which would complicate things: https://developers.google.com/drive/api/v3/manage-downloads#download_a_google_document
2. Use a server to periodically download the CSV and upload it to firebase cloud storage, where the client can access it. Servers can be configured to disregard CORS.
3. Use a server to proxy sheets access. This could be more responsive to spreadsheet updates. I don't think it makes sense as a solution for MSM since the spreadsheet hasn't actually been touched since launch...

[alexjball]

Immediate-term fix here: c7a47f9

[thadk]

This demo seems to still work: https://www.mapbox.com/impact-tools/sheet-mapper