skip authorization form

In some cases, one wants to auto-authorize users, instead of waiting for them to click the button. Provide this as an extension.

EDIT:

This will be done in tandem with the access_type parameter, in that:

• when access_type = "online":
  • "approval_prompt=force": the authorization prompt is shown every time;
  • "approval_prompt=auto": the authorization prompt shows up only for the first grant; it'll be auto-submitted afterwards;

default: force