fix: Switch to channel-ratio

- Use channel ratios instead of group ratios in all applicable places
- Start using the lowest channel ratio of the specified channel's groups

middleware/distributor.go

@@ -85,6 +85,16 @@ func Distribute() func(c *gin.Context) {
 }
 
 func SetupContextForSelectedChannel(c *gin.Context, channel *model.Channel, modelName string) {
+	// set minimal group ratio as channel_ratio
+	var minimalRatio float64
+	for _, grp := range strings.Split(channel.Group, ",") {
+		v := common.GetGroupRatio(grp)
+		if minimalRatio == 0 || v < minimalRatio {
+			minimalRatio = v
+		}
+	}
+	c.Set("channel_ratio", minimalRatio)
+
 	c.Set("channel", channel.Type)
 	c.Set("channel_id", channel.Id)
 	c.Set("channel_name", channel.Name)