fix auth completion and payment resume hardening

backend/internal/handler/auth_oauth_pending_flow_test.go

@@ -523,6 +523,68 @@ func TestExchangePendingOAuthCompletionLoginFalseFalseBindsIdentityWithoutAdopti
 	require.NotNil(t, storedSession.ConsumedAt)
 }
 
+func TestExchangePendingOAuthCompletionLoginWithoutDecisionStillBindsIdentity(t *testing.T) {
+	handler, client := newOAuthPendingFlowTestHandler(t, false)
+	ctx := context.Background()
+
+	userEntity, err := client.User.Create().
+		SetEmail("login-nodecision@example.com").
+		SetUsername("legacy-name").
+		SetPasswordHash("hash").
+		SetRole(service.RoleUser).
+		SetStatus(service.StatusActive).
+		Save(ctx)
+	require.NoError(t, err)
+
+	session, err := client.PendingAuthSession.Create().
+		SetSessionToken("login-nodecision-session-token").
+		SetIntent("login").
+		SetProviderType("linuxdo").
+		SetProviderKey("linuxdo").
+		SetProviderSubject("login-nodecision-123").
+		SetTargetUserID(userEntity.ID).
+		SetResolvedEmail(userEntity.Email).
+		SetBrowserSessionKey("login-nodecision-browser-session-key").
+		SetUpstreamIdentityClaims(map[string]any{
+			"username": "login-nodecision-user",
+		}).
+		SetLocalFlowState(map[string]any{
+			oauthCompletionResponseKey: map[string]any{
+				"access_token": "access-token",
+			},
+		}).
+		SetExpiresAt(time.Now().UTC().Add(10 * time.Minute)).
+		Save(ctx)
+	require.NoError(t, err)
+
+	recorder := httptest.NewRecorder()
+	ginCtx, _ := gin.CreateTestContext(recorder)
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/auth/oauth/pending/exchange", nil)
+	req.AddCookie(&http.Cookie{Name: oauthPendingSessionCookieName, Value: encodeCookieValue(session.SessionToken)})
+	req.AddCookie(&http.Cookie{Name: oauthPendingBrowserCookieName, Value: encodeCookieValue("login-nodecision-browser-session-key")})
+	ginCtx.Request = req
+
+	handler.ExchangePendingOAuthCompletion(ginCtx)
+
+	require.Equal(t, http.StatusOK, recorder.Code)
+
+	identity, err := client.AuthIdentity.Query().
+		Where(
+			authidentity.ProviderTypeEQ("linuxdo"),
+			authidentity.ProviderKeyEQ("linuxdo"),
+			authidentity.ProviderSubjectEQ("login-nodecision-123"),
+		).
+		Only(ctx)
+	require.NoError(t, err)
+	require.Equal(t, userEntity.ID, identity.UserID)
+
+	storedSession, err := client.PendingAuthSession.Query().
+		Where(pendingauthsession.IDEQ(session.ID)).
+		Only(ctx)
+	require.NoError(t, err)
+	require.NotNil(t, storedSession.ConsumedAt)
+}
+
 func TestExchangePendingOAuthCompletionBlocksBackendModeBeforeReturningTokenPayload(t *testing.T) {
 	handler, client := newOAuthPendingFlowTestHandlerWithDependencies(t, oauthPendingFlowTestHandlerOptions{
 		settingValues: map[string]string{