销售订单添加合同字段，销售订单form页面新增合同page页，优化/api/bfm_process_order/list接口添加合同信息处理。

sf_sale/models/sale_order.py

@@ -63,6 +63,10 @@ class ReSaleOrder(models.Model):
 
     model_display_version = fields.Char('模型展示版本', default="v1")
 
+    contract_document_id = fields.Many2one('documents.document', string='合同文件')
+    contract_file = fields.Binary(related='contract_document_id.datas', string='合同文件内容')
+    contract_file_name = fields.Char(related='contract_document_id.attachment_id.name', string='文件名')
+
     # 业务平台分配工厂后在智能工厂先创建销售订单
     def sale_order_create(self, company_id, delivery_name, delivery_telephone, delivery_address,
                           deadline_of_delivery, payments_way, pay_way, order_number, state='sale',