dvEncodeFormBody function
application/x-www-form-urlencoded body. Repeated keys are supported
because several mail APIs express multiple recipients that way.
Implementation
List<int> dvEncodeFormBody(List<(String, String)> fields) => utf8.encode(
fields
.map((field) =>
'${Uri.encodeQueryComponent(field.$1)}='
'${Uri.encodeQueryComponent(field.$2)}')
.join('&'),
);