Allow more checksum algorithms for each file

[aartoni]

At the moment, only one algorithm can be used at a time. Providing more checksum files can be useful when you want to provide one using a modern algo such as BLAKE2, along with a widely available one, such as SHA-256.

[mistydemeo]

We can definitely look into this. It'll be a bit of a reorganization since we have a few things that currently assume there's only one checksum algorithm. Do you mind if I ask what your usecase is? Do you have something specific that wants BLAKE2?

[aartoni]

I mainly provide BLAKE2 sums for Arch Linux packages. According to their documentation, BLAKE2 sums are to be preferred and should be provided by the upstream.

However, package managers from other distributions still rely on older algos (e.g., Debian, Alpine) and, in general, I'd like to keep providing SHA-256 for compatibility.