Enable creating documents as logged-in user (take 2)

[jfreda]

This is a follow-up to #508 to (hopefully!) enable creating documents on behalf of logged-in Hermes users when running Hermes as a service account with domain-wide authority.

Shared drive permissions and Google Docs notification settings are fun, and hopefully this can create documents with the same notification settings as when a user creates their own Google Docs, by first copying the template to a new temporary drafts folder as the logged-in user, and then using the service user to copy the file to the drafts folder (which should have less permissive permissions - will submit another PR for these doc updates).

New config attribute

google_workspace {
  ...
  // temporary_drafts_folder is a folder that will brieflly contain document
  // drafts before they are moved to the drafts_folder. This is used when
  // create_docs_as_user is true in the auth block, so document notification
  // settings will be the same as when a user creates their own document.
  temporary_drafts_folder = "my-temporary-drafts-folder-id"
  ...
  }
}