/usr/include/boost/network/message/ is in libcppnetlib-dev 0.11.0-1.1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/boost/network/message/directives/
/usr/include/boost/network/message/directives.hpp
/usr/include/boost/network/message/directives/detail/
/usr/include/boost/network/message/directives/detail/string_directive.hpp
/usr/include/boost/network/message/directives/detail/string_value.hpp
/usr/include/boost/network/message/directives/header.hpp
/usr/include/boost/network/message/directives/remove_header.hpp
/usr/include/boost/network/message/message_concept.hpp
/usr/include/boost/network/message/modifiers/
/usr/include/boost/network/message/modifiers/add_header.hpp
/usr/include/boost/network/message/modifiers/body.hpp
/usr/include/boost/network/message/modifiers/clear_headers.hpp
/usr/include/boost/network/message/modifiers/destination.hpp
/usr/include/boost/network/message/modifiers/remove_header.hpp
/usr/include/boost/network/message/modifiers/source.hpp
/usr/include/boost/network/message/traits/
/usr/include/boost/network/message/traits/body.hpp
/usr/include/boost/network/message/traits/destination.hpp
/usr/include/boost/network/message/traits/headers.hpp
/usr/include/boost/network/message/traits/source.hpp
/usr/include/boost/network/message/transformers/
/usr/include/boost/network/message/transformers.hpp
/usr/include/boost/network/message/transformers/selectors.hpp
/usr/include/boost/network/message/transformers/to_lower.hpp
/usr/include/boost/network/message/transformers/to_upper.hpp
/usr/include/boost/network/message/wrappers/
/usr/include/boost/network/message/wrappers.hpp
/usr/include/boost/network/message/wrappers/body.hpp
/usr/include/boost/network/message/wrappers/destination.hpp
/usr/include/boost/network/message/wrappers/headers.hpp
/usr/include/boost/network/message/wrappers/source.hpp