chore: add missing license headers

Author: yannham

libdd-trace-utils/src/change_buffer/buffer.rs

@@ -1,3 +1,6 @@
+// Copyright 2025-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
 use crate::change_buffer::utils::*;
 use crate::change_buffer::{ChangeBufferError, Result};
 

libdd-trace-utils/src/change_buffer/mod.rs

@@ -1,3 +1,6 @@
+// Copyright 2025-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
 //! Change buffer.
 //!
 //! A change buffer is a contiguous shared memory area between libdatadog and an external runtime.

libdd-trace-utils/src/change_buffer/operation.rs

@@ -1,3 +1,6 @@
+// Copyright 2025-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
 //! Change buffer operations.
 //!
 //! Operations are encoded in the change buffer, and provides an API on spans and their parts.

libdd-trace-utils/src/change_buffer/span_header.rs

@@ -1,3 +1,6 @@
+// Copyright 2025-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
 /// Fixed-layout span header for direct JS DataView access.
 ///
 /// JS creates a DataView over each span's header in WASM linear memory and writes fields directly.

libdd-trace-utils/src/change_buffer/trace.rs

@@ -1,3 +1,6 @@
+// Copyright 2025-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
 #[derive(Default)]
 pub struct Trace<T> {
     pub meta: Vec<(T, T)>,

libdd-trace-utils/src/change_buffer/utils.rs

@@ -1,3 +1,6 @@
+// Copyright 2025-Present Datadog, Inc. https://www.datadoghq.com/
+// SPDX-License-Identifier: Apache-2.0
+
 pub trait FromBytes: Sized {
     type Bytes: ?Sized;
     fn from_bytes(bytes: &[u8]) -> Self;