Decouple Handlers and Collections from protocol types (#765)

* Decouple Handlers and Collections (e.g. ToolsHandler and ToolsCollection) from Capabilities by promoting them to the options types.

Also, group all handlers in container classes, for server, I decided to move McpServerHandlers down to Mcp.Core and move the NotificationHandlers there too.

Also, Fix ListResourceTemplatesHandler issue.

* Add remarks for empty protocol capability types

* Keep JsonIgnore properties and mark them as Obsolete

* Continue supporting Obsolete members

* Update Obsolete messages to indicate the member will be removed

* Add EditorBrowsable Never to the remaining obsolete members

src/ModelContextProtocol.Core/Server/McpServerHandlers.cs

@@ -0,0 +1,177 @@
+using ModelContextProtocol.Protocol;
+
+namespace ModelContextProtocol.Server;
+
+/// <summary>
+/// Provides a container for handlers used in the creation of an MCP server.
+/// </summary>
+/// <remarks>
+/// <para>
+/// This class provides a centralized collection of delegates that implement various capabilities of the Model Context Protocol.
+/// Each handler in this class corresponds to a specific endpoint in the Model Context Protocol and
+/// is responsible for processing a particular type of message. The handlers are used to customize
+/// the behavior of the MCP server by providing implementations for the various protocol operations.
+/// </para>
+/// <para>
+/// When a client sends a message to the server, the appropriate handler is invoked to process it
+/// according to the protocol specification. Which handler is selected
+/// is done based on an ordinal, case-sensitive string comparison.
+/// </para>
+/// </remarks>
+public sealed class McpServerHandlers
+{
+    /// <summary>
+    /// Gets or sets the handler for <see cref="RequestMethods.ToolsList"/> requests.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// The handler should return a list of available tools when requested by a client.
+    /// It supports pagination through the cursor mechanism, where the client can make
+    /// repeated calls with the cursor returned by the previous call to retrieve more tools.
+    /// </para>
+    /// <para>
+    /// This handler works alongside any tools defined in the <see cref="McpServerTool"/> collection.
+    /// Tools from both sources will be combined when returning results to clients.
+    /// </para>
+    /// </remarks>
+    public McpRequestHandler<ListToolsRequestParams, ListToolsResult>? ListToolsHandler { get; set; }
+
+    /// <summary>
+    /// Gets or sets the handler for <see cref="RequestMethods.ToolsCall"/> requests.
+    /// </summary>
+    /// <remarks>
+    /// This handler is invoked when a client makes a call to a tool that isn't found in the <see cref="McpServerTool"/> collection.
+    /// The handler should implement logic to execute the requested tool and return appropriate results.
+    /// </remarks>
+    public McpRequestHandler<CallToolRequestParams, CallToolResult>? CallToolHandler { get; set; }
+
+    /// <summary>
+    /// Gets or sets the handler for <see cref="RequestMethods.PromptsList"/> requests.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// The handler should return a list of available prompts when requested by a client.
+    /// It supports pagination through the cursor mechanism, where the client can make
+    /// repeated calls with the cursor returned by the previous call to retrieve more prompts.
+    /// </para>
+    /// <para>
+    /// This handler works alongside any prompts defined in the <see cref="McpServerPrompt"/> collection.
+    /// Prompts from both sources will be combined when returning results to clients.
+    /// </para>
+    /// </remarks>
+    public McpRequestHandler<ListPromptsRequestParams, ListPromptsResult>? ListPromptsHandler { get; set; }
+
+    /// <summary>
+    /// Gets or sets the handler for <see cref="RequestMethods.PromptsGet"/> requests.
+    /// </summary>
+    /// <remarks>
+    /// This handler is invoked when a client requests details for a specific prompt that isn't found in the <see cref="McpServerPrompt"/> collection.
+    /// The handler should implement logic to fetch or generate the requested prompt and return appropriate results.
+    /// </remarks>
+    public McpRequestHandler<GetPromptRequestParams, GetPromptResult>? GetPromptHandler { get; set; }
+
+    /// <summary>
+    /// Gets or sets the handler for <see cref="RequestMethods.ResourcesTemplatesList"/> requests.
+    /// </summary>
+    /// <remarks>
+    /// The handler should return a list of available resource templates when requested by a client.
+    /// It supports pagination through the cursor mechanism, where the client can make
+    /// repeated calls with the cursor returned by the previous call to retrieve more resource templates.
+    /// </remarks>
+    public McpRequestHandler<ListResourceTemplatesRequestParams, ListResourceTemplatesResult>? ListResourceTemplatesHandler { get; set; }
+
+    /// <summary>
+    /// Gets or sets the handler for <see cref="RequestMethods.ResourcesList"/> requests.
+    /// </summary>
+    /// <remarks>
+    /// The handler should return a list of available resources when requested by a client.
+    /// It supports pagination through the cursor mechanism, where the client can make
+    /// repeated calls with the cursor returned by the previous call to retrieve more resources.
+    /// </remarks>
+    public McpRequestHandler<ListResourcesRequestParams, ListResourcesResult>? ListResourcesHandler { get; set; }
+
+    /// <summary>
+    /// Gets or sets the handler for <see cref="RequestMethods.ResourcesRead"/> requests.
+    /// </summary>
+    /// <remarks>
+    /// This handler is invoked when a client requests the content of a specific resource identified by its URI.
+    /// The handler should implement logic to locate and retrieve the requested resource.
+    /// </remarks>
+    public McpRequestHandler<ReadResourceRequestParams, ReadResourceResult>? ReadResourceHandler { get; set; }
+
+    /// <summary>
+    /// Gets or sets the handler for <see cref="RequestMethods.CompletionComplete"/> requests.
+    /// </summary>
+    /// <remarks>
+    /// This handler provides auto-completion suggestions for prompt arguments or resource references in the Model Context Protocol.
+    /// The handler processes auto-completion requests, returning a list of suggestions based on the
+    /// reference type and current argument value.
+    /// </remarks>
+    public McpRequestHandler<CompleteRequestParams, CompleteResult>? CompleteHandler { get; set; }
+
+    /// <summary>
+    /// Gets or sets the handler for <see cref="RequestMethods.ResourcesSubscribe"/> requests.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This handler is invoked when a client wants to receive notifications about changes to specific resources or resource patterns.
+    /// The handler should implement logic to register the client's interest in the specified resources
+    /// and set up the necessary infrastructure to send notifications when those resources change.
+    /// </para>
+    /// <para>
+    /// After a successful subscription, the server should send resource change notifications to the client
+    /// whenever a relevant resource is created, updated, or deleted.
+    /// </para>
+    /// </remarks>
+    public McpRequestHandler<SubscribeRequestParams, EmptyResult>? SubscribeToResourcesHandler { get; set; }
+
+    /// <summary>
+    /// Gets or sets the handler for <see cref="RequestMethods.ResourcesUnsubscribe"/> requests.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This handler is invoked when a client wants to stop receiving notifications about previously subscribed resources.
+    /// The handler should implement logic to remove the client's subscriptions to the specified resources
+    /// and clean up any associated resources.
+    /// </para>
+    /// <para>
+    /// After a successful unsubscription, the server should no longer send resource change notifications
+    /// to the client for the specified resources.
+    /// </para>
+    /// </remarks>
+    public McpRequestHandler<UnsubscribeRequestParams, EmptyResult>? UnsubscribeFromResourcesHandler { get; set; }
+
+    /// <summary>
+    /// Gets or sets the handler for <see cref="RequestMethods.LoggingSetLevel"/> requests.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// This handler processes <see cref="RequestMethods.LoggingSetLevel"/> requests from clients. When set, it enables
+    /// clients to control which log messages they receive by specifying a minimum severity threshold.
+    /// </para>
+    /// <para>
+    /// After handling a level change request, the server typically begins sending log messages
+    /// at or above the specified level to the client as notifications/message notifications.
+    /// </para>
+    /// </remarks>
+    public McpRequestHandler<SetLevelRequestParams, EmptyResult>? SetLoggingLevelHandler { get; set; }
+
+    /// <summary>Gets or sets notification handlers to register with the server.</summary>
+    /// <remarks>
+    /// <para>
+    /// When constructed, the server will enumerate these handlers once, which may contain multiple handlers per notification method key.
+    /// The server will not re-enumerate the sequence after initialization.
+    /// </para>
+    /// <para>
+    /// Notification handlers allow the server to respond to client-sent notifications for specific methods.
+    /// Each key in the collection is a notification method name, and each value is a callback that will be invoked
+    /// when a notification with that method is received.
+    /// </para>
+    /// <para>
+    /// Handlers provided via <see cref="NotificationHandlers"/> will be registered with the server for the lifetime of the server.
+    /// For transient handlers, <see cref="IMcpEndpoint.RegisterNotificationHandler"/> may be used to register a handler that can
+    /// then be unregistered by disposing of the <see cref="IAsyncDisposable"/> returned from the method.
+    /// </para>
+    /// </remarks>
+    public IEnumerable<KeyValuePair<string, Func<JsonRpcNotification, CancellationToken, ValueTask>>>? NotificationHandlers { get; set; }
+}