feat: RESP3 notifications support & Hitless notifications handling [CAE-1088] & [CAE-1072] (#3418)

- Adds support for handling push notifications with RESP3. 
- Using this support adds handlers for hitless upgrades.

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Hristo Temelski <hristo.temelski@redis.com>

internal/pool/hooks_test.go

@@ -0,0 +1,213 @@
+package pool
+
+import (
+	"context"
+	"errors"
+	"net"
+	"testing"
+	"time"
+)
+
+// TestHook for testing hook functionality
+type TestHook struct {
+	OnGetCalled  int
+	OnPutCalled  int
+	GetError     error
+	PutError     error
+	ShouldPool   bool
+	ShouldRemove bool
+}
+
+func (th *TestHook) OnGet(ctx context.Context, conn *Conn, isNewConn bool) error {
+	th.OnGetCalled++
+	return th.GetError
+}
+
+func (th *TestHook) OnPut(ctx context.Context, conn *Conn) (shouldPool bool, shouldRemove bool, err error) {
+	th.OnPutCalled++
+	return th.ShouldPool, th.ShouldRemove, th.PutError
+}
+
+func TestPoolHookManager(t *testing.T) {
+	manager := NewPoolHookManager()
+
+	// Test initial state
+	if manager.GetHookCount() != 0 {
+		t.Errorf("Expected 0 hooks initially, got %d", manager.GetHookCount())
+	}
+
+	// Add hooks
+	hook1 := &TestHook{ShouldPool: true}
+	hook2 := &TestHook{ShouldPool: true}
+
+	manager.AddHook(hook1)
+	manager.AddHook(hook2)
+
+	if manager.GetHookCount() != 2 {
+		t.Errorf("Expected 2 hooks after adding, got %d", manager.GetHookCount())
+	}
+
+	// Test ProcessOnGet
+	ctx := context.Background()
+	conn := &Conn{} // Mock connection
+
+	err := manager.ProcessOnGet(ctx, conn, false)
+	if err != nil {
+		t.Errorf("ProcessOnGet should not error: %v", err)
+	}
+
+	if hook1.OnGetCalled != 1 {
+		t.Errorf("Expected hook1.OnGetCalled to be 1, got %d", hook1.OnGetCalled)
+	}
+
+	if hook2.OnGetCalled != 1 {
+		t.Errorf("Expected hook2.OnGetCalled to be 1, got %d", hook2.OnGetCalled)
+	}
+
+	// Test ProcessOnPut
+	shouldPool, shouldRemove, err := manager.ProcessOnPut(ctx, conn)
+	if err != nil {
+		t.Errorf("ProcessOnPut should not error: %v", err)
+	}
+
+	if !shouldPool {
+		t.Error("Expected shouldPool to be true")
+	}
+
+	if shouldRemove {
+		t.Error("Expected shouldRemove to be false")
+	}
+
+	if hook1.OnPutCalled != 1 {
+		t.Errorf("Expected hook1.OnPutCalled to be 1, got %d", hook1.OnPutCalled)
+	}
+
+	if hook2.OnPutCalled != 1 {
+		t.Errorf("Expected hook2.OnPutCalled to be 1, got %d", hook2.OnPutCalled)
+	}
+
+	// Remove a hook
+	manager.RemoveHook(hook1)
+
+	if manager.GetHookCount() != 1 {
+		t.Errorf("Expected 1 hook after removing, got %d", manager.GetHookCount())
+	}
+}
+
+func TestHookErrorHandling(t *testing.T) {
+	manager := NewPoolHookManager()
+
+	// Hook that returns error on Get
+	errorHook := &TestHook{
+		GetError:   errors.New("test error"),
+		ShouldPool: true,
+	}
+
+	normalHook := &TestHook{ShouldPool: true}
+
+	manager.AddHook(errorHook)
+	manager.AddHook(normalHook)
+
+	ctx := context.Background()
+	conn := &Conn{}
+
+	// Test that error stops processing
+	err := manager.ProcessOnGet(ctx, conn, false)
+	if err == nil {
+		t.Error("Expected error from ProcessOnGet")
+	}
+
+	if errorHook.OnGetCalled != 1 {
+		t.Errorf("Expected errorHook.OnGetCalled to be 1, got %d", errorHook.OnGetCalled)
+	}
+
+	// normalHook should not be called due to error
+	if normalHook.OnGetCalled != 0 {
+		t.Errorf("Expected normalHook.OnGetCalled to be 0, got %d", normalHook.OnGetCalled)
+	}
+}
+
+func TestHookShouldRemove(t *testing.T) {
+	manager := NewPoolHookManager()
+
+	// Hook that says to remove connection
+	removeHook := &TestHook{
+		ShouldPool:   false,
+		ShouldRemove: true,
+	}
+
+	normalHook := &TestHook{ShouldPool: true}
+
+	manager.AddHook(removeHook)
+	manager.AddHook(normalHook)
+
+	ctx := context.Background()
+	conn := &Conn{}
+
+	shouldPool, shouldRemove, err := manager.ProcessOnPut(ctx, conn)
+	if err != nil {
+		t.Errorf("ProcessOnPut should not error: %v", err)
+	}
+
+	if shouldPool {
+		t.Error("Expected shouldPool to be false")
+	}
+
+	if !shouldRemove {
+		t.Error("Expected shouldRemove to be true")
+	}
+
+	if removeHook.OnPutCalled != 1 {
+		t.Errorf("Expected removeHook.OnPutCalled to be 1, got %d", removeHook.OnPutCalled)
+	}
+
+	// normalHook should not be called due to early return
+	if normalHook.OnPutCalled != 0 {
+		t.Errorf("Expected normalHook.OnPutCalled to be 0, got %d", normalHook.OnPutCalled)
+	}
+}
+
+func TestPoolWithHooks(t *testing.T) {
+	// Create a pool with hooks
+	hookManager := NewPoolHookManager()
+	testHook := &TestHook{ShouldPool: true}
+	hookManager.AddHook(testHook)
+
+	opt := &Options{
+		Dialer: func(ctx context.Context) (net.Conn, error) {
+			return &net.TCPConn{}, nil // Mock connection
+		},
+		PoolSize:    1,
+		DialTimeout: time.Second,
+	}
+
+	pool := NewConnPool(opt)
+	defer pool.Close()
+
+	// Add hook to pool after creation
+	pool.AddPoolHook(testHook)
+
+	// Verify hooks are initialized
+	if pool.hookManager == nil {
+		t.Error("Expected hookManager to be initialized")
+	}
+
+	if pool.hookManager.GetHookCount() != 1 {
+		t.Errorf("Expected 1 hook in pool, got %d", pool.hookManager.GetHookCount())
+	}
+
+	// Test adding hook to pool
+	additionalHook := &TestHook{ShouldPool: true}
+	pool.AddPoolHook(additionalHook)
+
+	if pool.hookManager.GetHookCount() != 2 {
+		t.Errorf("Expected 2 hooks after adding, got %d", pool.hookManager.GetHookCount())
+	}
+
+	// Test removing hook from pool
+	pool.RemovePoolHook(additionalHook)
+
+	if pool.hookManager.GetHookCount() != 1 {
+		t.Errorf("Expected 1 hook after removing, got %d", pool.hookManager.GetHookCount())
+	}
+}