Make it recognize not null constraints and set type to Unknown when the value is not recognized.

Note column not null constraints where not stored in pg_constraint before postgresl 18

pglab/crud/CrudModel.h

@@ -211,6 +211,13 @@ private:
 	bool callLoadData = false;
 
 	std::shared_ptr<Pgsql::Result> m_roData;
+
+    struct ColumnData
+    {
+        std::string name;
+        // identity allways or generated
+    };
+
     std::vector<PgAttribute> columnList; // list of columnMeta 1 to 1 with columns in m_roData.
 
 	PendingRowList m_pendingRowList;