Function channel_authorizing_group_key 

pub fn channel_authorizing_group_key(
    config: &Config,
    channel_type: &str,
    alias: &str,
    identity: &str,
) -> Option<String>

The peer_groups key that already authorizes identity, for reporting an already_bound result without guessing a name. Delegates to the crate-private identity_persist::authorizing_group_key.