Use Jose

[ulrikstrid]

Needs a release of jose with the changes (ulrikstrid/ocaml-jose#56). Release is here: ocaml/opam-repository#23366

Since most of the tests are already in Jose we can remove them from here and I should also cleanup the code a bit extra to remove unsafe things.

The test data is changed because Jose generates slightly different headers

The two big changes (except for the obvious code removal) is:

• We're moving to Yojson.Safe.t instead of Yojson.Basic.t.
• The internal key is now a Jose.Jwk.priv Jose.Jwk.t instead of a X509.Private_key.t. This is easily changed back however and we can hide that detail if we want to.

[ulrikstrid]

This is the other big change, moving from Basic to Safe since that's what is "supposed" to be used and also what Jose uses.

[dinosaure]

I'm not against deleting code but your PR adds a new dependency to letsencrypt. Is there any particular reason why we should use Jose instead of internal code (a feature we don't handle for example due to the limitation of our implementation)?

[ulrikstrid]

I understand your point of view, Jose doesn't have any dependencies we don't already have in this package I think so it's a minimal dependency to add so to speak. We have greater support for different keys in Jose that is currently supported here. And from a personal point of view it's good to de-duplicate code across the ecosystem since it's non-trivial. :)

[hannesm]

Thanks @ulrikstrid for the PR. I also think that deduplicating code is a good path forward. Unfortunately I've not found the time to review this PR (and look whether it increases dramatically build times or binary sizes).

[ulrikstrid]

No problem @hannesm, Jose had landed the needed improvements and I fixed some mirage-unfriendlyness while I was at it.
I can probably create a small app to see if there is a big size difference, I don't expect there to be much.