account_number is the account number of the account in state
auth_info_bytes is a protobuf serialization of an AuthInfo that matches the representation in TxRaw.
body_bytes is protobuf serialization of a TxBody that matches the representation in TxRaw.
chain_id is the unique identifier of the chain this transaction targets. It prevents signed transactions from being used on another chain by an attacker
SignDoc is the type used for generating sign bytes for SIGN_MODE_DIRECT.