Reduce logging level to WARN while flattening a signature field without N entry

DEVSIX-4920

Autoported commit.
Original commit hash: [b40620394]

Author: Evgeniy Prudnikov

itext.tests/itext.forms.tests/itext/forms/FlatteningTest.cs

@@ -41,6 +41,7 @@ source product.
 address: [email protected]
 */
 using System;
+using iText.Forms.Exceptions;
 using iText.Kernel.Pdf;
 using iText.Kernel.Utils;
 using iText.Test;
@@ -71,7 +72,7 @@ public virtual void FlatteningFormFieldNoSubtypeInAPTest() {
         }
 
         [NUnit.Framework.Test]
-        [LogMessage(iText.IO.Logs.IoLogMessageConstant.N_ENTRY_IS_REQUIRED_FOR_APPEARANCE_DICTIONARY)]
+        [LogMessage(FormsExceptionMessageConstant.N_ENTRY_IS_REQUIRED_FOR_APPEARANCE_DICTIONARY)]
         public virtual void FormFlatteningTestWithoutNEntry() {
             String filename = "formFlatteningTestWithoutNEntry";
             String src = sourceFolder + filename + ".pdf";

itext/itext.forms/itext/forms/PdfAcroForm.cs

@@ -833,7 +833,7 @@ public virtual void FlattenFields() {
                     }
                 }
                 else {
-                    LOGGER.LogError(iText.IO.Logs.IoLogMessageConstant.N_ENTRY_IS_REQUIRED_FOR_APPEARANCE_DICTIONARY);
+                    LOGGER.LogWarning(FormsExceptionMessageConstant.N_ENTRY_IS_REQUIRED_FOR_APPEARANCE_DICTIONARY);
                 }
                 PdfArray fFields = GetFields();
                 fFields.Remove(fieldObject);

itext/itext.forms/itext/forms/exceptions/FormsExceptionMessageConstant.cs

@@ -35,6 +35,8 @@ public sealed class FormsExceptionMessageConstant {
         public const String WRONG_FORM_FIELD_ADD_ANNOTATION_TO_THE_FIELD = "Wrong form field. Add annotation to the "
              + "field.";
 
+        public const String N_ENTRY_IS_REQUIRED_FOR_APPEARANCE_DICTIONARY = "\\N entry is required to be present in an appearance dictionary.";
+
         private FormsExceptionMessageConstant() {
         }
     }

itext/itext.io/itext/io/logs/IoLogMessageConstant.cs

@@ -281,6 +281,7 @@ public const String IMAGE_HAS_INCORRECT_OR_UNSUPPORTED_BASE_COLOR_SPACE_IN_INDEX
 
         public const String NUM_TREE_SHALL_NOT_END_WITH_KEY = "Number tree ends with a key which is invalid according to the PDF specification.";
 
+        [System.ObsoleteAttribute(@"Unused constant. Will be removed in 7.3")]
         public const String N_ENTRY_IS_REQUIRED_FOR_APPEARANCE_DICTIONARY = "\\N entry is required to be present in an appearance dictionary.";
 
         public const String OCCUPIED_AREA_HAS_NOT_BEEN_INITIALIZED = "Occupied area has not been initialized. {0}";

port-hash

@@ -1 +1 @@
-8db4d3e33a42e02dd631c24a1d7c216ef46ecf53
+b4062039402771737a56bddbc7f33a9bbfd177d6