Function transfer_intent_bytes 

pub fn transfer_intent_bytes(
    sender_agent_id: &str,
    recipient: &str,
    size_bytes: u64,
    declared_mime: &str,
    filename: &str,
    nonce: &str,
    issued_at_unix: i64,
) -> Result<Vec<u8>>

Canonical bytes signed by the sender when initiating a transfer.

Format:

spize-transfer-intent:v1
sender={sender_agent_id}
recipient={recipient}
size={size_bytes}
mime={declared_mime_or_empty}
filename={filename_or_empty}
nonce={nonce}
ts={issued_at_unix}