perf: 优化 BASE_SITE_URL OIDC 可以为空，实现多个不同端点访问时回调为当前访问的地址

apps/settings/serializers/auth/oidc.py

@@ -11,7 +11,8 @@ __all__ = [
 class CommonSettingSerializer(serializers.Serializer):
     # OpenID 公有配置参数 (version <= 1.5.8 或 version >= 1.5.8)
     BASE_SITE_URL = serializers.CharField(
-        required=False, allow_null=True, max_length=1024, label=_('Base site url')
+        required=False, allow_null=True, allow_blank=True,
+        max_length=1024, label=_('Base site url')
     )
     AUTH_OPENID_CLIENT_ID = serializers.CharField(
         required=False, max_length=1024, label=_('Client Id')