a813c9d8f3
Adds the settings pages to create OAuth2 apps also to the org settings and allows to create apps for orgs. Refactoring: the oauth2 related templates are shared for instance-wide/org/user, and the backend code uses `OAuth2CommonHandlers` to share code for instance-wide/org/user. Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>