TxTemplate

A transaction template bundling a builder with its sponsor and signer.

TxTemplate represents a transaction that is ready to be completed and signed. It bundles:

• builder: the TxBuilder with inputs, outputs, etc.
• sponsor: the address that pays fees (provides UTxOs for fees/collateral)
• signer: signs the completed transaction

This allows variations to be self-contained - each variation knows who will sign it.