chore: fixes mutability of the Repeat output (#2140)

## Overview
Closes #2139 

## Checklist

- [ ] New and updated code has appropriate documentation
- [ ] New and updated code has new and/or updated testing
- [ ] Required CI checks are passing
- [ ] Visual proof for any user facing features like CLI or
documentation updates
- [ ] Linked issues closed with keywords

pkg/namespace/namespace.go

@@ -148,7 +148,7 @@ func (n Namespace) IsPayForBlob() bool {
 func (n Namespace) Repeat(times int) []Namespace {
 	ns := make([]Namespace, times)
 	for i := 0; i < times; i++ {
-		ns[i] = n
+		ns[i] = n.deepCopy()
 	}
 	return ns
 }
@@ -180,3 +180,18 @@ func leftPad(b []byte, size int) []byte {
 	pad := make([]byte, size-len(b))
 	return append(pad, b...)
 }
+
+// deepCopy returns a deep copy of the Namespace object.
+func (n Namespace) deepCopy() Namespace {
+	// Create a deep copy of the ID slice
+	copyID := make([]byte, len(n.ID))
+	copy(copyID, n.ID)
+
+	// Create a new Namespace object with the copied fields
+	copyNamespace := Namespace{
+		Version: n.Version,
+		ID:      copyID,
+	}
+
+	return copyNamespace
+}

pkg/namespace/namespace_test.go

@@ -73,6 +73,19 @@ func TestNew(t *testing.T) {
 	}
 }
 
+// TestRepeatNonMutability ensures that the output of Repeat method is not mutated when the original namespace is mutated.
+func TestRepeatNonMutability(t *testing.T) {
+	n := 10
+	namespace := Namespace{Version: NamespaceVersionMax, ID: []byte{1, 2, 3, 4}}
+	repeated := namespace.Repeat(n)
+	// mutate the original namespace
+	namespace.ID[0] = 5
+	// ensure the repeated namespaces are not mutated
+	for i := 0; i < n; i++ {
+		assert.NotEqual(t, repeated[i], namespace)
+	}
+}
+
 func TestNewV0(t *testing.T) {
 	type testCase struct {
 		name    string