Encode into b64 to avoid illegal xml encoding when sending to Azure (#1425)

* Encode into b64 to avoid illegal xml encoding when sending to Azure

* Revert "Encode into b64 to avoid illegal xml encoding when sending to Azure"

This reverts commit d50de941da.

* HtmlEncode strings if they use multi-byte characters

* Add serializer to event processor

* Rename to used class

* Formatting

* PR feedback

src/Core/Utilities/EncodedStringConverter.cs

@@ -0,0 +1,35 @@
+using System;
+using Newtonsoft.Json;
+
+namespace Bit.Core.Utilities
+{
+    public class EncodedStringConverter : JsonConverter
+    {
+        public override bool CanConvert(Type objectType) => objectType == typeof(string);
+
+        public override object ReadJson(JsonReader reader, Type objectType, object existingValue, JsonSerializer serializer)
+        {
+            if (reader.TokenType == JsonToken.Null)
+            {
+                return existingValue;
+            }
+
+            var value = reader.Value as string;
+            return System.Net.WebUtility.HtmlDecode(value);
+        }
+
+        public override void WriteJson(JsonWriter writer, object value, JsonSerializer serializer)
+        {
+            if (value == null)
+            {
+                if (serializer.NullValueHandling == NullValueHandling.Include)
+                {
+                    writer.WriteNull();
+                }
+                return;
+            }
+
+            writer.WriteValue(System.Net.WebUtility.HtmlEncode((string)value));
+        }
+    }
+}