Implement layout element to draw signature appearance

DEVSIX-7770

Author: AnhelinaM

commons/src/main/java/com/itextpdf/commons/utils/DateTimeUtil.java

@@ -216,6 +216,17 @@ public static long getCurrentTimeZoneOffset(Date date) {
         return tz.getOffset(date.getTime());
     }
 
+    /**
+     * Converts {@link Calendar} date to string of "yyyy.MM.dd HH:mm:ss z" format.
+     *
+     * @param date to convert.
+     *
+     * @return string date value.
+     */
+    public static String dateToString(Calendar date) {
+        return new SimpleDateFormat("yyyy.MM.dd HH:mm:ss z").format(date.getTime());
+    }
+
     private static DateFormat initParserSDF(String pattern) {
         final SimpleDateFormat parserSDF = new SimpleDateFormat(pattern);
         parserSDF.setCalendar(new GregorianCalendar());

forms/src/main/java/com/itextpdf/forms/fields/PdfFormAnnotation.java

@@ -135,10 +135,11 @@ public static void processDirtyAnnotations(PdfFormField parentField, boolean thr
             if (field.getChildFields().size() > 0 && field.getChildFormFields().size() == 0) {
                 boolean shouldBeMerged = true;
 
-                // If parent is radio button we don't care about field related keys, always merge
+                // If parent is radio button or signature we don't care about field related keys, always merge
                 // If not - go over all fields to compare with parent's fields
                 if (!(PdfName.Btn.equals(parentField.getFormType()) &&
-                        parentField.getFieldFlag(PdfButtonFormField.FF_RADIO))) {
+                        parentField.getFieldFlag(PdfButtonFormField.FF_RADIO)) &&
+                        !PdfName.Sig.equals(parentField.getFormType())) {
                     if (formDict.containsKey(PdfName.T)) {
                         // We only want to perform the merge if field doesn't contain any name (even empty one)
                         continue;