Use Boost's `outcome::result<T>` type as the return type for function that can return failure or success

*References:*

1. https://www.boost.org/doc/libs/develop/libs/outcome/doc/html/index.html
2. Building your own error codes: https://akrzemi1.wordpress.com/2017/07/12/your-own-error-code/
3. outcome::result<T> Variant-1: https://www.boost.org/doc/libs/develop/libs/outcome/doc/html/reference/aliases/boost_result.html
4. outcome::result<T> Variant-2: https://www.boost.org/doc/libs/develop/libs/outcome/doc/html/reference/types/basic_result.html