Add Backup & Restore page with Google Drive integration

Server/API/GoogleDriveCallbackController.cs

@@ -0,0 +1,58 @@
+using Microsoft.AspNetCore.Authorization;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.AspNetCore.Mvc;
+using Remotely.Server.Services;
+using Remotely.Shared.Entities;
+using System.Threading.Tasks;
+
+namespace Remotely.Server.API;
+
+[Route("api/[controller]")]
+[ApiController]
+[Authorize]
+public class GoogleDriveCallbackController : ControllerBase
+{
+    private readonly IGoogleDriveService _googleDriveService;
+    private readonly UserManager<RemotelyUser> _userManager;
+
+    public GoogleDriveCallbackController(
+        IGoogleDriveService googleDriveService,
+        UserManager<RemotelyUser> userManager)
+    {
+        _googleDriveService = googleDriveService;
+        _userManager = userManager;
+    }
+
+    [HttpGet]
+    public async Task<IActionResult> Callback([FromQuery] string code, [FromQuery] string state)
+    {
+        if (string.IsNullOrEmpty(code))
+        {
+            return BadRequest("Authorization code is missing.");
+        }
+
+        if (string.IsNullOrEmpty(state))
+        {
+            return BadRequest("State parameter is missing.");
+        }
+
+        var user = await _userManager.GetUserAsync(User);
+        if (user is null)
+        {
+            return Unauthorized();
+        }
+
+        // Validate the OAuth state token to prevent CSRF attacks.
+        var validatedUserId = _googleDriveService.ValidateOAuthState(state);
+        if (validatedUserId is null || validatedUserId != user.Id)
+        {
+            return BadRequest("Invalid or expired OAuth state token.");
+        }
+
+        var redirectUri = $"{Request.Scheme}://{Request.Host}/api/googledrivecallback";
+
+        await _googleDriveService.ExchangeCodeForTokenAsync(user.Id, code, redirectUri);
+
+        return LocalRedirect("/backup");
+    }
+}

Server/Components/Layout/NavMenu.razor

@@ -68,6 +68,11 @@
                         <span class="oi oi-pencil" aria-hidden="true"></span> User Options
                     </NavLink>
                 </li>
+                <li class="nav-item px-3">
+                    <NavLink class="nav-link" href="backup">
+                        <span class="oi oi-hard-drive" aria-hidden="true"></span> Backup
+                    </NavLink>
+                </li>
 
             </Authorized>
         </AuthorizeView>