currency is an ISO 4217 code.
Only USD is supported today.
Amounts
Amounts are integers in the currency’s smallest unit, e.g. cents forUSD.
125000 is $1,250.00.
Parse amounts as integers and keep them as integers. Converting to a
floating-point number of dollars loses precision.
Signs
A transaction’samount is signed: credits are positive and debits are
negative. Do not derive direction from anything else.