Fix Type serialization for MongoDB provider

src/persistence/Elsa.Persistence.MongoDb/Serializers/TypeSerializer.cs

@@ -0,0 +1,28 @@
+using System;
+using Elsa.Models;
+using MongoDB.Bson.Serialization;
+using Rebus.Extensions;
+
+namespace Elsa.Persistence.MongoDb.Serializers
+{
+    public class TypeSerializer : IBsonSerializer<Type>
+    {
+        public static TypeSerializer Instance { get; } = new();
+        public Type ValueType => typeof(Variables);
+        public void Serialize(BsonSerializationContext context, BsonSerializationArgs args, object value) => Serialize(context, args, (Type) value);
+
+        public void Serialize(BsonSerializationContext context, BsonSerializationArgs args, Type value)
+        {
+            var typeName = value.GetSimpleAssemblyQualifiedName();
+            context.Writer.WriteString(typeName);
+        }
+
+        object IBsonSerializer.Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args) => Deserialize(context, args);
+
+        public Type Deserialize(BsonDeserializationContext context, BsonDeserializationArgs args)
+        {
+            var typeName = context.Reader.ReadString();
+            return typeName is not null and not "" ? Type.GetType(typeName)! : default!;
+        }
+    }
+}

src/persistence/Elsa.Persistence.MongoDb/Services/DatabaseRegister.cs

@@ -63,6 +63,7 @@ private static void RegisterSerializers()
             BsonSerializer.RegisterSerializer(VariablesSerializer.Instance);
             BsonSerializer.RegisterSerializer(JObjectSerializer.Instance);
             BsonSerializer.RegisterSerializer(ObjectSerializer.Instance);
+            BsonSerializer.RegisterSerializer(TypeSerializer.Instance);
             BsonSerializer.RegisterSerializer(new InstantSerializer());
         }
     }