TF-2520 Convert email object to html to perform print on browser

Signed-off-by: dab246 <tdvu@linagora.com>

core/lib/data/constants/constant.dart

@@ -2,4 +2,5 @@ class Constant {
   static const acceptHeaderDefault = 'application/json';
   static const contentTypeHeaderDefault = 'application/json';
   static const pdfMimeType = 'application/pdf';
+  static const textHtmlMimeType = 'text/html';
 }

core/lib/data/model/print_attachment.dart

@@ -2,19 +2,19 @@
 import 'package:equatable/equatable.dart';
 
 class PrintAttachment with EquatableMixin {
-  final String iconSvg;
+  final String iconBase64Data;
   final String name;
   final String size;
 
   PrintAttachment({
-    required this.iconSvg,
+    required this.iconBase64Data,
     required this.name,
     required this.size
   });
 
   @override
   List<Object?> get props => [
-    iconSvg,
+    iconBase64Data,
     name,
     size
   ];