Refactor HTTP method handling and cleanup

Refactored HTTP method handling by introducing a `ToHttpMethod`
extension method in `HttpExtensions.cs` to convert string
representations of HTTP methods to `HttpMethod` objects.
Replaced manual `HttpMethod` instantiation with the new
extension method in `InvokeRecActionCommandHandler` for
improved readability and reusability.

Removed unused `using` directives from `HttpExtensions.cs`
and cleaned up the `namespace` declaration. Added a `using`
directive for `ReC.Application.Common` in
`InvokeRecActionCommand.cs` to support the new extension method.

src/ReC.Application/Common/HttpExtensions.cs

@@ -1,11 +1,17 @@
-using System;
-using System.Collections.Generic;
-using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
-
-namespace ReC.Application.Common;
+namespace ReC.Application.Common;
 
 public static class HttpExtensions
 {
+    public static HttpMethod ToHttpMethod(this string method) => method.ToUpper() switch
+    {
+        "GET" => HttpMethod.Get,
+        "POST" => HttpMethod.Post,
+        "PUT" => HttpMethod.Put,
+        "DELETE" => HttpMethod.Delete,
+        "PATCH" => HttpMethod.Patch,
+        "HEAD" => HttpMethod.Head,
+        "OPTIONS" => HttpMethod.Options,
+        "TRACE" => HttpMethod.Trace,
+        _ => throw new ArgumentException($"Invalid HTTP method: {method}", nameof(method)),
+    };
 }