feat: add EnvelopeKeyRedirController to redirect /EnvelopeKey/{*path} to /Envelope/{*path}

EnvelopeGenerator.Web/Controllers/EnvelopeKeyRedirController.cs

@@ -0,0 +1,13 @@
+using Microsoft.AspNetCore.Mvc;
+
+namespace EnvelopeGenerator.Web.Controllers;
+
+[Route("EnvelopeKey")]
+public class EnvelopeKeyRedirController : Controller
+{
+    /// <summary>
+    /// Redirects /EnvelopeKey/{*path} -> /Envelope/{*path}
+    /// </summary>
+    [HttpGet("{*path}")]
+    public IActionResult RedirectToEnvelope(string path) => Redirect($"/Envelope/{path}");
+}