add: 子类开发获取分片策略，支持传参

src/Mysql/MysqlClusterBase.php

@@ -318,13 +318,21 @@ abstract class MysqlClusterBase
      *
      * @return array
      */
-    private static function getDatabaseShardingIndex()
+    protected static function getDatabaseShardingIndex($dbShardingColumnValue = 0, $dbShardingCompatColumnValue = 0)
     {
         // 未使用分库
         if (!static::SHARDING_DATABASE) {
             return 0;
         }
 
+        if(!empty($dbShardingColumnValue)) {
+            self::$dbShardingColumnValue = $dbShardingColumnValue;
+        }
+
+        if(!empty($dbShardingCompatColumnValue)) {
+            self::$dbShardingCompatColumnValue = $dbShardingCompatColumnValue;
+        }
+
         self::getDbShardingCount();
 
         $dbShardingIndex = 0;