SPDX standardizes how source code conveys its copyright and licensing
information. See https://spdx.github.io/spdx-spec/1-rationale/ . SPDX
tags are adopted in many large projects, including things like the Linux
kernel.

The general convention in the codebase is to compare the non-constant
value/string with the constant value/string, not the other way around.

Given all conditional bodies only contain a return, the use of else here
isn't necessary.

This has the benefit of consistently vertically aligning the names.

There's nothing within this function that requires a copy of the string
to be made, so we can make use of a non-owning view

This isn't used anywhere in the translation unit, so we can remove it.

Since we target C++17, we can collapse the namespaces into a single
declaration specifier.