fyi.opensocial.provisionGroup

Host-level: an app creates a group for a person and gets its own OAuth session on it. Authenticated twice: the person asking, by service auth from their PDS (they become the founder), and the app, by OAuth client authentication in the body (a client assertion for a confidential client) with a DPoP proof in the `DPoP` header, exactly as at the token endpoint. The app must be one this host provisions for. Returns the group and a token response bound to the proof's key, issued to the app's client id: refreshed, listed and revoked like any other session on the group.