the-biergarten-app/web/backend/API/API.Core/Controllers/NotFoundController.cs

using Microsoft.AspNetCore.Mvc;

namespace API.Core.Controllers
{
    /// <summary>
    /// Handles requests that do not match any other route, used as the application's fallback controller.
    /// </summary>
    /// <remarks>
    /// Excluded from API explorer/Swagger output via <c>[ApiExplorerSettings(IgnoreApi = true)]</c>.
    /// Wired up as the fallback target via <c>app.MapFallbackToController("Handle404", "NotFound")</c> in <c>Program.cs</c>.
    /// </remarks>
    [ApiController]
    [ApiExplorerSettings(IgnoreApi = true)]
    [Route("error")] // required
    public class NotFoundController : ControllerBase
    {
        /// <summary>
        /// Returns a generic 404 response for any request that did not match a defined route.
        /// </summary>
        /// <returns>A <c>404 Not Found</c> result with a JSON body containing a "Route not found." message.</returns>
        [HttpGet("404")] //required
        public IActionResult Handle404()
        {
            return NotFound(new { message = "Route not found." });
        }
    }
}