Create project files

yawaflua.WebSockets/Attributes/WebSocketAttribute.cs

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+using JetBrains.Annotations;
+using Microsoft.AspNetCore.Mvc;
+
+namespace yawaflua.WebSockets.Attributes;
+
+/// <summary>
+/// Attribute that marks WebSocket endpoint handlers. 
+/// Applied to classes or methods to define WebSocket route templates.
+/// 
+/// Usage examples:
+/// [WebSocket("/chat")] - basic route
+/// [WebSocket("/notifications/{userId}")] - route with parameter
+/// [WebSocket("/game/{roomId}/players")] - complex route
+/// </summary>
+/// <remarks>
+/// Inherits from ASP.NET Core's RouteAttribute to leverage standard routing syntax.
+/// When applied to a class, defines the base path for all WebSocket endpoints in controller.
+/// When applied to methods, defines specific sub-routes (requires class-level base path).
+/// </remarks>
+[AttributeUsage(AttributeTargets.Method | AttributeTargets.Class)]
+public class WebSocketAttribute : RouteAttribute
+{
+    /// <summary>
+    /// Original route template specified in attribute
+    /// </summary>
+    public string Template { get; }
+    
+    /// <summary>
+    /// Creates WebSocket route definition
+    /// </summary>
+    /// <param name="path">Route template using ASP.NET Core syntax:
+    /// - Static: "/status"
+    /// - Parameters: "/user/{id}"
+    /// - Constraints: "/file/{name:alpha}"
+    /// - Optional: "/feed/{category?}"</param>
+    public WebSocketAttribute([RouteTemplate]string path) : base(path)
+    {
+        Template = path;
+    }
+}