Function verify_channel_jekt_v2 

pub fn verify_channel_jekt_v2(
    public_key: &[u8],
    msgid: &str,
    source_agent: &str,
    source_uid: &str,
    source_channel: &str,
    target_agent: &str,
    ts_secs: i64,
    message: &str,
    sig_b64: &str,
) -> bool

Verify a v2 cross-channel signature against the public key published for source_uid. false, never a panic, for anything malformed.