addMultipartAlternative method
Adds a part with the multipart/alternative subtype.
Optionally specify the plainText and the htmlText. Note that
you need to specify either neither or both.
Same as addPart(mediaSubtype: MediaSubtype.multipartAlternative) when
no texts are given.
Implementation
PartBuilder addMultipartAlternative({String? plainText, String? htmlText}) {
final partBuilder =
addPart(mediaSubtype: MediaSubtype.multipartAlternative);
if (plainText != null && htmlText != null) {
partBuilder
..addTextPlain(plainText)
..addTextHtml(htmlText);
}
return partBuilder;
}