feat(mail): initial support for ms-tnef (winmail.dat) body part

Fixes #2242
Fixes #4503

UI/MailPartViewers/UIxMailPartViewer.m

@@ -189,9 +189,19 @@
                          [self className], @"type",
                        type, @"contentType",
                        [[self generateResponse] contentAsString], @"content",
+                       [self filenameForDisplay], @"filename",
+                       [self preferredPathExtension], @"extension",
+                       [[self sizeFormatter] stringForObjectValue: [bodyInfo objectForKey: @"size"]], @"size",
+                       [self pathToAttachment], @"viewURL",
+                       [self pathForDownload], @"downloadURL",
                        nil];
 }
 
+- (NSDictionary *) attachmentIds
+{
+  return attachmentIds;
+}
+
 //
 // Attachment IDs are used to replace CID from HTML content
 // with their MIME parts when viewing an HTML mail with