feat(rcs): migrate all RCS APIs from rainyun-go-sdk

- 35 endpoints across 14 files, response structs split for reuse
- Reuse RcsRecord/Node/Plan/OsInfo/UsageData across list/detail/create
- Fix source bugs: {id} path placeholders, missing / in firewall pos path,
  missing body in ChargeRcsTrafic, resp vs &resp
- Add HTTPMethod_PATCH, common.BasicOperationResponse, VncConnectionInfo

apis/rcs/nat.go

@@ -0,0 +1,39 @@
+package rcs
+
+import (
+	"fmt"
+
+	"github.com/XingfenD/rainyun_api_go_sdk/apis/common"
+	"github.com/XingfenD/rainyun_api_go_sdk/constant"
+)
+
+type AddRcsNatPortMappingRequest struct {
+	PortIn   int    `json:"port_in"`   // >= 1 <= 65535
+	PortOut  int    `json:"port_out"`  // >= 10000 <= 60000
+	PortType string `json:"port_type"` // tcp/udp/tcp_udp
+	Tag      string `json:"tag"`       // 可选
+}
+
+type DeleteRcsNatPortMappingRequest struct {
+	NatID int `json:"nat_id"`
+}
+
+func (s *RcsService) AddRcsNatPortMapping(id int, req *AddRcsNatPortMappingRequest) (*common.BasicOperationResponse, error) {
+	path := fmt.Sprintf("/product/rcs/%d/nat", id)
+
+	var resp common.BasicOperationResponse
+	err := s.client.Do(constant.HTTPMethod_POST, path, nil, req, &resp)
+	return &resp, err
+}
+
+func (s *RcsService) DeleteRcsNatPortMapping(id int, req *DeleteRcsNatPortMappingRequest) (*common.BasicOperationResponse, error) {
+	path := fmt.Sprintf("/product/rcs/%d/nat", id)
+
+	var resp common.BasicOperationResponse
+	querys, err := common.MarshalQueryParams(req)
+	if err != nil {
+		return nil, err
+	}
+	err = s.client.Do(constant.HTTPMethod_DELETE, path, querys, nil, &resp)
+	return &resp, err
+}