Refactor project structure in solution

Replaced "EnvelopeGenerator.WebUI" with "EnvelopeGenerator.Server" and "EnvelopeGenerator.WebUI.Client" with "EnvelopeGenerator.Server.Client". Updated project entries, solution configuration platforms, and nested projects to reflect these changes.

EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Services/AuthService.cs

@@ -0,0 +1,81 @@
+using System.Net;
+using System.Net.Http.Json;
+using EnvelopeGenerator.WebUI.Client.Options;
+using Microsoft.Extensions.Options;
+
+namespace EnvelopeGenerator.WebUI.Client.Services;
+
+public enum EnvelopeLoginResult { Success, InvalidCode, NotFound, Error }
+
+public enum SenderLoginResult { Success, InvalidCredentials, Error }
+
+public class AuthService(HttpClient http, IOptions<ApiOptions> apiOptions)
+{
+    private readonly ApiOptions _api = apiOptions.Value;
+
+    /// <summary>
+    /// Checks whether the current user holds a valid receiver token for the given envelope key.
+    /// Calls GET /api/auth/check/envelope/{envelopeKey}.
+    /// </summary>
+    public async Task<bool> CheckEnvelopeAccessAsync(string envelopeKey, CancellationToken cancel = default)
+    {
+        var response = await http.GetAsync($"{_api.BaseUrl}/api/auth/check/envelope/{Uri.EscapeDataString(envelopeKey)}", cancel);
+        return response.StatusCode == HttpStatusCode.OK;
+    }
+
+    /// <summary>
+    /// Submits the access code for the given envelope key.
+    /// Calls POST /api/Auth/envelope-receiver/{key} with multipart/form-data.
+    /// On success the API sets an authentication cookie automatically.
+    /// </summary>
+    public async Task<EnvelopeLoginResult> LoginEnvelopeReceiverAsync(string envelopeKey, string accessCode, CancellationToken cancel = default)
+    {
+        var form = new MultipartFormDataContent();
+        form.Add(new StringContent(accessCode), "AccessCode");
+
+        var response = await http.PostAsync(
+            $"{_api.BaseUrl}/api/Auth/envelope-receiver/{Uri.EscapeDataString(envelopeKey)}",
+            form, cancel);
+
+        return response.StatusCode switch
+        {
+            HttpStatusCode.OK => EnvelopeLoginResult.Success,
+            HttpStatusCode.Unauthorized => EnvelopeLoginResult.InvalidCode,
+            HttpStatusCode.NotFound => EnvelopeLoginResult.NotFound,
+            _ => EnvelopeLoginResult.Error
+        };
+    }
+
+    /// <summary>
+    /// Removes the per-envelope receiver cookie for the given envelope key.
+    /// Calls POST /api/auth/logout/envelope/{envelopeKey}.
+    /// </summary>
+    public async Task<bool> LogoutEnvelopeReceiverAsync(string envelopeKey, CancellationToken cancel = default)
+    {
+        var response = await http.PostAsync(
+            $"{_api.BaseUrl}/api/auth/logout/envelope/{Uri.EscapeDataString(envelopeKey)}",
+            null, cancel);
+        return response.IsSuccessStatusCode;
+    }
+
+    /// <summary>
+    /// Authenticates a sender user with username and password.
+    /// Calls POST /api/auth?cookie=true with JSON body.
+    /// On success the API sets an authentication cookie automatically.
+    /// </summary>
+    public async Task<SenderLoginResult> LoginSenderAsync(string username, string password, CancellationToken cancel = default)
+    {
+        var requestBody = new { username, password };
+
+        var response = await http.PostAsJsonAsync(
+            $"{_api.BaseUrl}/api/auth?cookie=true",
+            requestBody, cancel);
+
+        return response.StatusCode switch
+        {
+            HttpStatusCode.OK => SenderLoginResult.Success,
+            HttpStatusCode.Unauthorized => SenderLoginResult.InvalidCredentials,
+            _ => SenderLoginResult.Error
+        };
+    }
+}