is_eq : _
Url
Url :: # (opaque)
Where a download is fetched from: https://<host>/<path>, with no
credentials, query or fragment. A quoted URL is checked as it compiles. One
built by interpolation, as in "https://example.org/${version}/tool", is
assembled as it is and checked with the rest of the configuration.
Only text can be interpolated: write ${system.to_str()} for a System, or
use Recipes.file with a {system} placeholder.
from_quote : Str -> Try(Url, [BadQuotedBytes(Str)])
A URL assembled from text that is checked elsewhere. The whole configuration is validated after lowering, this URL with it.