Summary:
Implementing export to excel and send to Google Drive feature.
As part of this feature few things were implemented:
- Server side google authentication exposed on url: (docs, docs-s, or localhost:8080)/auth/google
- Exporting grist documents as an excel file (xlsx)
- Storing exported grist document (in excel format) in Google Drive as a spreadsheet document.
Server side google authentication requires one new environmental variables
- GOOGLE_CLIENT_SECRET (required) used by authentication handler
Test Plan: Browser tests for exporting to excel.
Reviewers: paulfitz, dsagal
Reviewed By: paulfitz
Differential Revision: https://phab.getgrist.com/D2924
