[#5624456C086AC9FCEBCB6A8C414C4A252BEC1105]
Return the known scheme for a non-normalized string, if known
scheme string_to_scheme(core::string_view s) noexcept;
If the string does not identify a known scheme, the value scheme::unknown is returned.
scheme = ALPHA *( ALPHA / DIGIT / "+" / "-" / "." )