feat: support upstream model fetch for advanced custom channels (#5971)

* feat: support upstream model fetch for advanced custom channels

* fix: add advanced custom routes as separate groups

* fix: select advanced custom route entry before adding

---------

Co-authored-by: CaIon <i@caion.me>

model/channel.go

@@ -962,6 +962,11 @@ func (channel *Channel) ValidateSettings() error {
 			return err
 		}
 	}
+	if channel.Type == constant.ChannelTypeAdvancedCustom && channelOtherSettings.UpstreamModelUpdateCheckEnabled {
+		if _, ok := channelOtherSettings.AdvancedCustom.ModelListRoute(); !ok {
+			return fmt.Errorf("advanced custom channels require a %s route when upstream model update checks are enabled", dto.AdvancedCustomModelListPath)
+		}
+	}
 	return nil
 }