- Added `status_code` expectations in serialization and deserialization tests.
- Introduced tests for invalid `status_code` handling in `MessageSerializer`.
- Updated test cases to include `MessageStatus::OK` for payload validation and round-trip scenarios.
- Added comprehensive unit tests for `MessageSerializer` in `MessageSerializerTest.cpp`.
- Included `MessageSerializerTest.cpp` in `test/CMakeLists.txt`.