add support for strict_type connections

Currently the strict_type=True option on the Meta class for a node is ignored and the connections end up having nullable values in the edge list. If you override the connection_class to set the strict_type on the connection, the SQLAlchemyConnectionField constructor fails because it does not unwrap the NonNull from the node before trying to set up the sort.

Ideally it should be possible to set the strict_type option on the connection via metadata on the node class.

先追蹤 node Meta.strict_type 設定如何傳遞到連線，以及當節點型別為 NonNull 時 SQLAlchemyConnectionField 如何建構排序。重現 issue 中描述的 nullable edge 清單行為和建構函式失敗。完成標準是節點中繼資料可以在連線上設定 strict_type，且欄位建構函式能正確處理 NonNull 節點。

由索引模型根據 Issue 內容生成。