type DID string

# The Delegation payload MUST describe the authorization claims, who is involved, and its validity period.
type Payload struct {
    # Issuer DID (sender)
    iss DID
    # Audience DID (receiver)
    aud DID
    # Principal that the chain is about (the Subject)
    sub optional DID

    # The Command to eventually invoke
    cmd String

    # The delegation policy
    # It doesn't seem possible to represent it with a schema.
    pol Any

    # A unique, random nonce
    nonce Bytes

    # Arbitrary Metadata
    meta {String : Any}

    # "Not before" UTC Unix Timestamp in seconds (valid from), 53-bits integer
    nbf optional Int
    # The timestamp at which the Invocation becomes invalid
    exp nullable Int
}