* Adding L1RollupTxId field to Transactions
* Adding rollup transactions signing key config and bug fixing within api.go. Signing key and endpoint will be removed when go handles batch fetching
* Adding L1MessageSender to Transaction
* Adding logic to omit L1MessageSender in encoding / decoding when nil and never use it in hash computation
Co-authored-by: ben-chain <ben@pseudonym.party>