Add some kind of ACL-based sharing with co-coaches

[jmarantz]

Could be via Firebase database layer, or an API to Google Sheets.

[jmarantz]

Various ways to go about this.

1. Use a pure firebase DB layer and implement own ACLs. This might support multiple coaches having the same view of a single game, but I think it might be a lot of work, and I don't know if there's a lot of value in that.

2. Rely on Google Drive for ACLs, and use Google Drive's REST API as database. This might be interesting, if the native format was a Google Sheet, and so player lineups and position setup could be done in the spreadsheet.

3. A hybrid, where you start with a spreadsheet but dup the data into Firebase DB. This approach is described in https://sites.google.com/site/scriptsexamples/new-connectors-to-google-services/firebase/tutorials/read-and-write-data-in-firebase-from-apps-script

I'm kind of inclined to have the data live in Google Drive, but maybe the approach in #3 is a good way to transmit the data into Firebase app. The question is how do we then persist the game data back into the spreadsheet (and is that even an important direction)?

[jmarantz]

Cloud platform ACLs: https://cloud.google.com/storage/docs/access-control/lists