Improve progress reporting (#145)

* Improve progress reporting

- Enable injecting an `IProgress<>` into a tool call to report progress when the client has supplied a progress token
- Add a custom type for ProgressToken and ProgressNotification to map to the schema
- Simplify RequestId to match ProgressToken's shape
- Serialize StdioClientTransport's SendMessageAsync implementation
- Add strongly-typed names for all request methods
- Change all request IDs created by McpJsonRpcEndpoint to include a guid for that endpoint

* Address PR feedback

src/ModelContextProtocol/Protocol/Messages/ProgressNotification.cs

@@ -0,0 +1,108 @@
+using System.ComponentModel;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace ModelContextProtocol.Protocol.Messages;
+
+/// <summary>
+/// An out-of-band notification used to inform the receiver of a progress update for a long-running request.
+/// <see href="https://github.com/modelcontextprotocol/specification/blob/main/schema/">See the schema for details</see>
+/// </summary>
+[JsonConverter(typeof(Converter))]
+public class ProgressNotification
+{
+    /// <summary>
+    /// The progress token which was given in the initial request, used to associate this notification with the request that is proceeding.
+    /// </summary>
+    public required ProgressToken ProgressToken { get; init; }
+
+    /// <summary>
+    /// The progress thus far. This should increase every time progress is made, even if the total is unknown.
+    /// </summary>
+    public required ProgressNotificationValue Progress { get; init; }
+
+    /// <summary>Provides a <see cref="JsonConverter"/> for <see cref="ProgressNotification"/>.</summary>
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public sealed class Converter : JsonConverter<ProgressNotification>
+    {
+        /// <inheritdoc />
+        public override ProgressNotification? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+        {
+            ProgressToken? progressToken = null;
+            float? progress = null;
+            float? total = null;
+            string? message = null;
+            
+            while (reader.Read() && reader.TokenType != JsonTokenType.EndObject)
+            {
+                if (reader.TokenType == JsonTokenType.PropertyName)
+                {
+                    var propertyName = reader.GetString();
+                    reader.Read();
+                    switch (propertyName)
+                    {
+                        case "progressToken":
+                            progressToken = (ProgressToken)JsonSerializer.Deserialize(ref reader, options.GetTypeInfo(typeof(ProgressToken)))!;
+                            break;
+
+                        case "progress":
+                            progress = reader.GetSingle();
+                            break;
+
+                        case "total":
+                            total = reader.GetSingle();
+                            break;
+
+                        case "message":
+                            message = reader.GetString();
+                            break;
+                    }
+                }
+            }
+
+            if (progress is null)
+            {
+                throw new JsonException("Missing required property 'progress'.");
+            }
+
+            if (progressToken is null)
+            {
+                throw new JsonException("Missing required property 'progressToken'.");
+            }
+
+            return new ProgressNotification
+            {
+                ProgressToken = progressToken.GetValueOrDefault(),
+                Progress = new ProgressNotificationValue()
+                {
+                    Progress = progress.GetValueOrDefault(),
+                    Total = total,
+                    Message = message
+                }
+            };
+        }
+
+        /// <inheritdoc />
+        public override void Write(Utf8JsonWriter writer, ProgressNotification value, JsonSerializerOptions options)
+        {
+            writer.WriteStartObject();
+
+            writer.WritePropertyName("progressToken");
+            JsonSerializer.Serialize(writer, value.ProgressToken, options.GetTypeInfo(typeof(ProgressToken)));
+
+            writer.WriteNumber("progress", value.Progress.Progress);
+
+            if (value.Progress.Total is { } total)
+            {
+                writer.WriteNumber("total", total);
+            }
+
+            if (value.Progress.Message is { } message)
+            {
+                writer.WriteString("message", message);
+            }
+
+            writer.WriteEndObject();
+        }
+    }
+}