Keycloak role mapper for PeerTube

If we want to do automatic role mapping from Keycloak to PeerTube we need to create a mapper with the values:

• 2 - User (default)
• 1- Moderator
• 0 - Administrator

See https://www.npmjs.com/package/peertube-plugin-auth-openid-connect

See the role definitions in table portal#44 (comment 65684).