[VCL] Sign generated v-card upon using a profile

Closes https://code.vereign.com/code/signing-service-agent/issues/31

javascript/src/helpers/mailparser.js

@@ -122,6 +122,27 @@ export function fixNewLines(mime) {
   return mime.replace(newline, "\r\n");
 }
 
+export function extractMessageID(mime) {
+  if (mime.startsWith("\r\n")) {
+    mime = mime.substring(2); //should not happen
+  }
+  const headersEndIndex = mime.indexOf("\r\n\r\n"); //the first empty line
+  if (headersEndIndex < 0) {
+    return null;
+  }
+  const mimeHeaders = mime.substring(0, headersEndIndex);
+  const headers = libmime.decodeHeaders(mimeHeaders);
+  let messageId = headers["Message-ID"];
+  if (Array.isArray(messageId) && messageId.length > 0) {
+    messageId = messageId[0];
+  }
+  if (messageId && typeof messageId === "string") {
+    messageId = messageId.replace(/^</, '').replace(/>$/, '');
+    return messageId;
+  }
+  return null;
+}
+
 export function parseMIME(mime) {
   let mimeStart = 0;
   let headersEnd = mime.indexOf("\r\n\r\n"); //the first empty line