feat: add wechat authentication

Tiku.Application/Auth/AuthContracts.cs

@@ -36,6 +36,12 @@ public sealed record SmsLoginRequest(
     string? IpAddress,
     string? UserAgent);
 
+public sealed record WechatLoginRequest(
+    Guid TenantId,
+    string Code,
+    string? IpAddress,
+    string? UserAgent);
+
 public sealed record RefreshSessionRequest(
     string RefreshToken,
     string? IpAddress,

Tiku.Application/Auth/AuthExceptions.cs

@@ -16,3 +16,6 @@ public sealed class SessionRevokedException()
 
 public sealed class SmsRateLimitedException()
     : AuthException("sms_rate_limited", "SMS verification requests are rate limited.");
+
+public sealed class AuthProviderNotConfiguredException(string provider)
+    : AuthException("auth_provider_not_configured", $"The {provider} auth provider is not configured.");

Tiku.Application/Auth/IAuthService.cs

@@ -10,6 +10,14 @@ public interface IAuthService
         SmsLoginRequest request,
         CancellationToken cancellationToken = default);
 
+    Task<AuthenticatedUser> LoginWithWechatWebAsync(
+        WechatLoginRequest request,
+        CancellationToken cancellationToken = default);
+
+    Task<AuthenticatedUser> LoginWithWechatMiniAppAsync(
+        WechatLoginRequest request,
+        CancellationToken cancellationToken = default);
+
     Task<AuthTokenPair> RefreshAsync(
         RefreshSessionRequest request,
         CancellationToken cancellationToken = default);

Tiku.Application/Auth/IWechatOAuthClient.cs

@@ -0,0 +1,26 @@
+namespace Tiku.Application.Auth;
+
+public sealed record WechatProviderOptions(
+    string AppId,
+    string AppSecret);
+
+public sealed record WechatIdentity(
+    string OpenId,
+    string? UnionId,
+    string? Nickname,
+    string? AvatarUrl,
+    string? SessionKey,
+    string RawJson);
+
+public interface IWechatOAuthClient
+{
+    Task<WechatIdentity> ExchangeWebCodeAsync(
+        WechatProviderOptions options,
+        string code,
+        CancellationToken cancellationToken = default);
+
+    Task<WechatIdentity> ExchangeMiniAppCodeAsync(
+        WechatProviderOptions options,
+        string code,
+        CancellationToken cancellationToken = default);
+}