MM-11118: disallow deleting direct or group channels (#9054)

api4/channel.go

@@ -638,6 +638,11 @@ func deleteChannel(c *Context, w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	if channel.Type == model.CHANNEL_DIRECT || channel.Type == model.CHANNEL_GROUP {
+		c.Err = model.NewAppError("deleteChannel", "api.channel.delete_channel.type.invalid", nil, "", http.StatusBadRequest)
+		return
+	}
+
 	if channel.Type == model.CHANNEL_OPEN && !c.App.SessionHasPermissionToChannel(c.Session, channel.Id, model.PERMISSION_DELETE_PUBLIC_CHANNEL) {
 		c.SetPermissionError(model.PERMISSION_DELETE_PUBLIC_CHANNEL)
 		return