SOLIDUI: support apps to have index of public resources

[jesscmoore]

Description

Solid based apps need to be serve files that are publicly or auth user accessible. This requires the url of files shared as public/auth accessible to be written to an index file setup for that app. This way the app can query every url in the file and show those files which are still public/auth readable. To do this, we need a onPermissionGranted callback that returns the recipientType of the permission grant.

Why

So that as a user, my app shows me files that are accessible to me because they are auth user/publicly readable.

Closing Criteria

Checklist for closing the issue:

• provides a callback function on GrantPermissionUI() that runs when permission is granted for auth users or public.
• includes the python utility script in solidui template to allow developers to have an index pod service account with an index ttl file for storing urls of files shared to auth users or public

Context

See related issue in Exper app:

Issue 22 - Experience app https://github.com/privacyeng/exper/issues/22