feat(ip): assign copyright to the Linux Foundation (#10)

Adopt the new attribution information for contributions to
CloudNativePG:

```
Copyright © contributors to CloudNativePG, established as
CloudNativePG a Series of LF Projects, LLC.
```

Adopt the SPDX format for Apache License 2.0

Signed-off-by: Marco Nenciarini <marco.nenciarini@enterprisedb.com>

Author: mnencia

http_test.cpp

@@ -1,5 +1,6 @@
 /*
-Copyright The CloudNativePG Contributors
+Copyright © contributors to CloudNativePG, established as
+CloudNativePG a Series of LF Projects, LLC.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -12,6 +13,8 @@ distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
+
+SPDX-License-Identifier: Apache-2.0
 */
 
 #include "httplib.h"