Add project files.

Middlewares/DependencyCheckMiddleware.cs

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+using MTWireGuard.Pages;
+using MTWireGuard.Repositories;
+using Razor.Templating.Core;
+using System.Globalization;
+
+namespace MTWireGuard.Middlewares
+{
+    public class DependencyCheckMiddleware
+    {
+        private readonly RequestDelegate _next;
+        private readonly IMikrotikRepository API;
+
+        public DependencyCheckMiddleware(RequestDelegate next, IMikrotikRepository mikrotik)
+        {
+            _next = next;
+            API = mikrotik;
+        }
+
+        public async Task InvokeAsync(HttpContext context)
+        {
+            bool Error = false;
+
+            string? IP = Environment.GetEnvironmentVariable("MT_IP");
+            string? USER = Environment.GetEnvironmentVariable("MT_USER");
+            string? PASS = Environment.GetEnvironmentVariable("MT_PASS");
+            string? PUBLICIP = Environment.GetEnvironmentVariable("MT_PUBLIC_IP");
+
+            ErrorModel errorModel = new();
+            Dictionary<string, object> ViewBag = new();
+
+            if (string.IsNullOrEmpty(IP) || string.IsNullOrEmpty(USER) || string.IsNullOrEmpty(PUBLICIP))
+            {
+                ViewBag["Title"] = "Environment variables are not set!";
+                ViewBag["Message"] = "Please set \"MT_IP\", \"MT_USER\", \"MT_PASS\", \"MT_PUBLIC_IP\" variables in container environment.";
+                Error = true;
+            }
+            else
+            {
+                if (context.Request.Path.Value == "/Login")
+                {
+                    await _next(context);
+                    return;
+                }
+                try
+                {
+                    bool APIEnabled = await API.TryConnectAsync();
+                }
+                catch (Exception ex)
+                {
+                    ViewBag["Title"] = "Error connecting to the router api!";
+                    ViewBag["Message"] = ex.Message;
+                    Error = true;
+                }
+            }
+
+            if (Error)
+            {
+                var html = await RazorTemplateEngine.RenderAsync("/Pages/Error.cshtml", errorModel, ViewBag);
+                context.Response.StatusCode = 200;
+                await context.Response.WriteAsync(html);
+                return;
+            }
+            else
+            {
+                await _next(context);
+            }
+        }
+    }
+
+    public static class DependencyCheckMiddlewareExtensions
+    {
+        public static IApplicationBuilder UseDependencyCheck(this IApplicationBuilder builder)
+        {
+            return builder.UseMiddleware<DependencyCheckMiddleware>();
+        }
+    }
+}