clio should have a config field type that has to be a path, and it should expand homedir etc.

[willmurphyscode]

What would you like to be added:

Clio should know that certain config fields represent paths on the local filesystem, and should do some common expansions, for example ~, $HOME, and $TMPDIR, so that these can be expanded.

Probably we want something like type LocalPath string in the config, and then config structs in clio applications can declare fields to be LocalPath instead of string in order to get the expansion behavior.

Why is this needed:

anchore/grype#2024
anchore/grype#2599

[kzantow]

This would need to be a new type, which ends up being a bit annoying at times:type LocalPath string (no =; it can't use aliasing, because we need a new type to implement the PostLoad interface). It would basically work like secrets do, just to update the value using homedir or whatnot.