test(web): add Discord auth and platform identity tests

- DiscordAuthServiceTests: authorize URL, token exchange, profile fetch
- PlatformIdentityTests: Telegram fallback, Discord identity, avatar URL

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/GmRelay.Bot.Tests/Web/DiscordAuthServiceTests.cs

@@ -0,0 +1,139 @@
+using System.Net;
+using System.Text.Json;
+using GmRelay.Web;
+using GmRelay.Web.Services;
+using Microsoft.Extensions.Configuration;
+
+namespace GmRelay.Bot.Tests.Web;
+
+public class DiscordAuthServiceTests
+{
+    [Fact]
+    public void BuildAuthorizeUrl_GeneratesCorrectUrl()
+    {
+        var config = new ConfigurationBuilder()
+            .AddInMemoryCollection(new Dictionary<string, string?>
+            {
+                ["Discord:ClientId"] = "12345",
+                ["Discord:ClientSecret"] = "secret",
+                ["Discord:RedirectUri"] = "https://example.com/callback"
+            })
+            .Build();
+
+        var service = new DiscordAuthService(new TestHttpClientFactory(), config);
+        var url = service.BuildAuthorizeUrl("state123");
+
+        Assert.Contains("client_id=12345", url);
+        Assert.Contains("response_type=code", url);
+        Assert.Contains("state=state123", url);
+        Assert.Contains("https%3A%2F%2Fexample.com%2Fcallback", url);
+    }
+
+    [Fact]
+    public void BuildAuthorizeUrl_WithMissingConfig_ThrowsInvalidOperationException()
+    {
+        var config = new ConfigurationBuilder().Build();
+        var service = new DiscordAuthService(new TestHttpClientFactory(), config);
+
+        Assert.Throws<InvalidOperationException>(() => service.BuildAuthorizeUrl("state"));
+    }
+
+    [Fact]
+    public async Task ExchangeCodeAsync_WithValidCode_ReturnsUser()
+    {
+        var handler = new TestHttpMessageHandler((request) =>
+        {
+            if (request.RequestUri?.AbsolutePath == "/api/oauth2/token")
+            {
+                var response = new DiscordTokenResponse("access_123", "Bearer", 604800, "identify");
+                return new HttpResponseMessage(HttpStatusCode.OK)
+                {
+                    Content = new StringContent(JsonSerializer.Serialize(response))
+                };
+            }
+
+            if (request.RequestUri?.AbsolutePath == "/api/users/@me")
+            {
+                var user = new DiscordUser("98765", "TestUser", "0", "avatar123", null);
+                return new HttpResponseMessage(HttpStatusCode.OK)
+                {
+                    Content = new StringContent(JsonSerializer.Serialize(user))
+                };
+            }
+
+            return new HttpResponseMessage(HttpStatusCode.NotFound);
+        });
+
+        var config = new ConfigurationBuilder()
+            .AddInMemoryCollection(new Dictionary<string, string?>
+            {
+                ["Discord:ClientId"] = "client",
+                ["Discord:ClientSecret"] = "secret",
+                ["Discord:RedirectUri"] = "https://example.com/callback"
+            })
+            .Build();
+
+        var factory = new TestHttpClientFactory(handler);
+        var service = new DiscordAuthService(factory, config);
+
+        var result = await service.ExchangeCodeAsync("valid_code");
+
+        Assert.NotNull(result);
+        Assert.Equal("98765", result.Id);
+        Assert.Equal("TestUser", result.Username);
+        Assert.Equal("https://cdn.discordapp.com/avatars/98765/avatar123.png", result.AvatarUrl);
+    }
+
+    [Fact]
+    public async Task ExchangeCodeAsync_WithInvalidCode_ReturnsNull()
+    {
+        var handler = new TestHttpMessageHandler((request) =>
+        {
+            return new HttpResponseMessage(HttpStatusCode.BadRequest);
+        });
+
+        var config = new ConfigurationBuilder()
+            .AddInMemoryCollection(new Dictionary<string, string?>
+            {
+                ["Discord:ClientId"] = "client",
+                ["Discord:ClientSecret"] = "secret",
+                ["Discord:RedirectUri"] = "https://example.com/callback"
+            })
+            .Build();
+
+        var factory = new TestHttpClientFactory(handler);
+        var service = new DiscordAuthService(factory, config);
+
+        var result = await service.ExchangeCodeAsync("invalid_code");
+
+        Assert.Null(result);
+    }
+
+    private class TestHttpClientFactory : IHttpClientFactory
+    {
+        private readonly HttpMessageHandler? _handler;
+
+        public TestHttpClientFactory(HttpMessageHandler? handler = null)
+        {
+            _handler = handler;
+        }
+
+        public HttpClient CreateClient(string name) =>
+            _handler is not null ? new HttpClient(_handler) : new HttpClient();
+    }
+
+    private class TestHttpMessageHandler : HttpMessageHandler
+    {
+        private readonly Func<HttpRequestMessage, HttpResponseMessage> _handler;
+
+        public TestHttpMessageHandler(Func<HttpRequestMessage, HttpResponseMessage> handler)
+        {
+            _handler = handler;
+        }
+
+        protected override Task<HttpResponseMessage> SendAsync(HttpRequestMessage request, CancellationToken cancellationToken)
+        {
+            return Task.FromResult(_handler(request));
+        }
+    }
+}

tests/GmRelay.Bot.Tests/Web/PlatformIdentityTests.cs

@@ -0,0 +1,114 @@
+using System.Security.Claims;
+using GmRelay.Web.Services;
+
+namespace GmRelay.Bot.Tests.Web;
+
+public class PlatformIdentityTests
+{
+    [Fact]
+    public void TryGetPlatformIdentity_TelegramUser_ReturnsTelegramPlatform()
+    {
+        var user = new ClaimsPrincipal(new ClaimsIdentity(new[]
+        {
+            new Claim(ClaimTypes.NameIdentifier, "12345"),
+            new Claim("TelegramId", "12345")
+        }));
+
+        var result = user.TryGetPlatformIdentity(out var platform, out var externalUserId);
+
+        Assert.True(result);
+        Assert.Equal("Telegram", platform);
+        Assert.Equal("12345", externalUserId);
+    }
+
+    [Fact]
+    public void TryGetPlatformIdentity_TelegramUserWithPlatformClaim_ReturnsTelegramPlatform()
+    {
+        var user = new ClaimsPrincipal(new ClaimsIdentity(new[]
+        {
+            new Claim(ClaimTypes.NameIdentifier, "12345"),
+            new Claim("Platform", "Telegram")
+        }));
+
+        var result = user.TryGetPlatformIdentity(out var platform, out var externalUserId);
+
+        Assert.True(result);
+        Assert.Equal("Telegram", platform);
+        Assert.Equal("12345", externalUserId);
+    }
+
+    [Fact]
+    public void TryGetPlatformIdentity_DiscordUser_ReturnsDiscordPlatform()
+    {
+        var user = new ClaimsPrincipal(new ClaimsIdentity(new[]
+        {
+            new Claim(ClaimTypes.NameIdentifier, "98765"),
+            new Claim("DiscordId", "98765"),
+            new Claim("Platform", "Discord")
+        }));
+
+        var result = user.TryGetPlatformIdentity(out var platform, out var externalUserId);
+
+        Assert.True(result);
+        Assert.Equal("Discord", platform);
+        Assert.Equal("98765", externalUserId);
+    }
+
+    [Fact]
+    public void TryGetPlatformIdentity_UnknownUser_ReturnsFalse()
+    {
+        var user = new ClaimsPrincipal(new ClaimsIdentity(new[]
+        {
+            new Claim(ClaimTypes.Name, "Anonymous")
+        }));
+
+        var result = user.TryGetPlatformIdentity(out _, out _);
+        Assert.False(result);
+    }
+
+    [Fact]
+    public void TryGetDiscordId_DiscordUser_ReturnsTrue()
+    {
+        var user = new ClaimsPrincipal(new ClaimsIdentity(new[]
+        {
+            new Claim("DiscordId", "123")
+        }));
+
+        var result = user.TryGetDiscordId(out var discordId);
+        Assert.True(result);
+        Assert.Equal("123", discordId);
+    }
+
+    [Fact]
+    public void TryGetDiscordId_TelegramUser_ReturnsFalse()
+    {
+        var user = new ClaimsPrincipal(new ClaimsIdentity(new[]
+        {
+            new Claim("TelegramId", "123")
+        }));
+
+        var result = user.TryGetDiscordId(out _);
+        Assert.False(result);
+    }
+
+    [Fact]
+    public void GetAvatarUrl_DiscordUserWithAvatar_ReturnsUrl()
+    {
+        var user = new ClaimsPrincipal(new ClaimsIdentity(new[]
+        {
+            new Claim("AvatarUrl", "https://cdn.discordapp.com/avatars/1/abc.png")
+        }));
+
+        var result = user.GetAvatarUrl();
+        Assert.Equal("https://cdn.discordapp.com/avatars/1/abc.png", result);
+    }
+
+    [Fact]
+    public void GetAvatarUrl_UserWithoutAvatar_ReturnsNull()
+    {
+        var user = new ClaimsPrincipal(new ClaimsIdentity(Array.Empty<Claim>()));
+
+        var result = user.GetAvatarUrl();
+        Assert.Null(result);
+    }
+}