The usual convention to create new object is to prefix `New*` so
this commit renames the `WorkerClientError`. Initially I thought
it would be `NewWorkerClientError()` but looking at the package
prefix it seems unneeded, i.e. `clienterrors.New()` already
provides enough context it seems and it's the only error we
construct.
We could consider renaming it to `clienterror` (singular) too
but that could be a followup.
I would also like to make `clienterror.Error` implement the
`error` interface but that should be a followup to make this
(mechanical) rename trivial to review.
Create a resolver to fetch the contents of a
remote file which can be used at build time.
The initial usecase for this resolver is to
resolve remote gpgkeys but the resolver has
been made more generic for general files.
