user-guide: update gdrive setup guide

[maxhora]

• New optional param to turn on Trash_Only option for gdrive remote;
• DVC starts to provide default client id and secret to access GDrive API;
• Service account support.

[jorgeorpinel]

Please link to corresponding core repo PR.

[shcheklein]

@jorgeorpinel I doubt the will be very informative, ask me any questions or let's do a call so that I can share the context

[jorgeorpinel]

Is it treeverse/dvc/pull/3269?

[jorgeorpinel]

I'm just trying to find a place to comment on the name of the remote modify parameters being used e.g. projectname should probably be project_name.

[shcheklein]

Yes, and one or two to gdrive.py after that.

[shcheklein]

@jorgeorpinel projectname was way before GDrive - it's common for Google tools I believe

[jorgeorpinel]

K. also credentailpath. We have underscores in most other param names from what I can see. Not a huge deal I guess.

[jorgeorpinel]

Oh yeah sorry I was looking at the Google Cloud Storage section! Never mind...

[maxhora]

Please link to corresponding core repo PR.

It is related to last 3 commits https://github.com/iterative/dvc/commits?author=maxhora