Fix `Jsonify` issues, including preserving `unknown` types

[jpwilliams]

Summary

Jsonify is used to represent a step output going through serialization as it passes to and from an Inngest Server in JSON. This used to be part of the type-fest package, but we removed that when introducing support for TypeScript 5.4 in #500, as our version support range for TS exceeded what was provided by the type-fest package.

As part of that, we've pulled Jsonify into our code. There are some issues (in the related section) we can now fix much more easily.

The issue that motivated this change (#509) would also have been solved by allowing a developer to provide types that describe how the output of a step is transformed. This is available, but is a rare ask and needs time to implement.

Checklist

• [ ] ~Added a docs PR that references this PR~ N/A Docs only outline that this is a helper, not specific behaviour
• [x] Added unit/integration tests
• [x] Added changesets if applicable

Related

• Fixes #509 (marking this as a fix, but again, note that middleware typing can also solve different strains of this issue)
• Fixes #456
• Fixes #513
• Fixes #98

[changeset-bot[bot]]

🦋 Changeset detected

Latest commit: aac0d42c3ec06edd54e428f3e86780c33376ca9e

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

| Name | Type | | ------- | ----- | | inngest | Patch |

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[inngest-release-bot]

A user has added the prerelease/inngest label, so this PR will be published to npm with the tag pr-512. It will be updated with the latest changes as you push commits to this PR.

You can install this prerelease version with:

npm install inngest@pr-512

The last release was built and published from aac0d42c3ec06edd54e428f3e86780c33376ca9e.