"to": "<checksummed address>",
"value": 0, // Value in wei
"data": "<0x prefixed hex string>",
"operation": 0, // 0 CALL, 1 DELEGATE_CALL
"gasToken": "<checksummed address>", // Token address (hold by the Safe) to be used as a refund to the sender, if `null` is Ether
"safeTxGas": 0, // Max gas to use in the transaction
"baseGas": 0, // Gast costs not related to the transaction execution (signature check, refund payment...)
"gasPrice": 0, // Gas price used for the refund calculation
"refundReceiver": "<checksummed address>", //Address of receiver of gas payment (or `null` if tx.origin)
"nonce": 0, // Nonce of the Safe, transaction cannot be executed until Safe's nonce is not equal to this nonce
"contractTransactionHash": "string", // Contract transaction hash calculated from all the field
"sender": "<checksummed address>", // Owner of the Safe proposing the transaction. Must match one of the signatures
"signature": "<0x prefixed hex string>", // One or more ethereum ECDSA signatures of the `contractTransactionHash` as an hex string
"origin": "string" // Give more information about the transaction, e.g. "My Custom Safe app"