feat(secondary): Send NOTIFY messages after zone transfer (#7901)

* feat(secondary): Send NOTIFY messages after zone transfer

- Modified TransferIn() method to accept a transfer.Transfer parameter
- Added NOTIFY message sending after successful zone transfer in secondary plugin
- Updated Update() method to pass the transfer handler through the zone update cycle
- Added comprehensive tests for the secondary notify functionality

Closes #5669

Signed-off-by: liucongran <liucongran327@gmail.com>

* fix(secondary): Fix TransferIn method call in test

Update test to pass nil parameter to TransferIn method after signature change

Signed-off-by: liucongran <liucongran327@gmail.com>

* refactor(secondary): Clean up imports and add helper methods

- Reorder imports for consistency
- Add hasSOA() and getSOA() helper methods to Zone
- Remove unnecessary blank lines in tests

Signed-off-by: liucongran <liucongran327@gmail.com>

* fix(test): Fix variable declaration in secondary test

Change corefile variable assignment to use short declaration syntax (:=)
to fix compilation error.

Signed-off-by: liucongran <liucongran327@gmail.com>

* refactor(secondary): Use getSOA helper method in shouldTransfer

Replace direct SOA access with getSOA() helper method for consistency.

Signed-off-by: liucongran <liucongran327@gmail.com>

---------

Signed-off-by: liucongran <liucongran327@gmail.com>
Co-authored-by: liucongran <liucongran@cestc.cn>

plugin/secondary/setup.go

@@ -10,6 +10,7 @@ import (
 	clog "github.com/coredns/coredns/plugin/pkg/log"
 	"github.com/coredns/coredns/plugin/pkg/parse"
 	"github.com/coredns/coredns/plugin/pkg/upstream"
+	"github.com/coredns/coredns/plugin/transfer"
 )
 
 var log = clog.NewWithPlugin("secondary")
@@ -22,6 +23,17 @@ func setup(c *caddy.Controller) error {
 		return plugin.Error("secondary", err)
 	}
 
+	s := &Secondary{file.File{Zones: zones}}
+	var x *transfer.Transfer
+	c.OnStartup(func() error {
+		t := dnsserver.GetConfig(c).Handler("transfer")
+		if t != nil {
+			x = t.(*transfer.Transfer)
+			s.Xfer = x // if found this must be OK.
+		}
+		return nil
+	})
+
 	// Add startup functions to retrieve the zone and keep it up to date.
 	for i := range zones.Names {
 		n := zones.Names[i]
@@ -36,7 +48,7 @@ func setup(c *caddy.Controller) error {
 						dur := time.Millisecond * 250
 						max := time.Second * 10
 						for {
-							err := z.TransferIn()
+							err := z.TransferIn(x)
 							if err == nil {
 								break
 							}
@@ -52,7 +64,7 @@ func setup(c *caddy.Controller) error {
 							default:
 							}
 						}
-						z.Update(updateShutdown)
+						z.Update(updateShutdown, x)
 					}()
 				})
 				return nil
@@ -65,7 +77,8 @@ func setup(c *caddy.Controller) error {
 	}
 
 	dnsserver.GetConfig(c).AddPlugin(func(next plugin.Handler) plugin.Handler {
-		return Secondary{file.File{Next: next, Zones: zones}}
+		s.Next = next
+		return s
 	})
 
 	return nil