Add default role for new oidc user

[trueleo]

Description

In 0.7 we explicitly need to have 'group' claim in the ID Token for role assignment to work. In some cases it may be desirable to give default role to new user logging into the page.

Proposal

create a special role parseable:public that can be configured with role api. In cases where group claim is not found or group claim is insufficient we fallback to assigning this role to user so that console works for them.