[Ingest Manager] Add route for package installation by upload

[skh]

Summary

Partially implements #70582

• Adds the route POST /api/ingest_manager/epm/packages that takes a buffer as body, which should contain the package archive to be installed.
• Refactors the existing route handlers for package installation so that "install by upload" and "install from registry" are clearly distinguishable.
• Adds an integration test for the new endpoint.
• Archive verification and package installation are not implemented yet. This change intentionally only adds the API endpoint.

How to test this

curl -X POST -u elastic:changeme http://localhost:5601/api/ingest_manager/epm/packages --data @./tmp/packages/foo.tar.gz -H 'kbn-xsrf: xyz' -H 'Content-Type: application/gzip'

should respond with

{"response":"package upload was received ok, but not installed (not implemented yet)"}

No actual package installation takes place yet. The integrity or file type of the archive (foo.tar.gz) isn't verified yet.

Choice of route

With this change,

• POST /api/ingest_manager/epm/packages/{pkgkey} is used to install a package from the registry, and
• POST /api/ingest_manager/epm/packages for installing by direct upload.

The initial reason was that the existing endpoint already uses the POST body to optionally send the { force: true|false } parameter, so it can't be used to upload a file, but it would of course be possible to refactor that and move the force parameter to URL params instead. That way, the same route could be used for both ways to install a package.

After thinking a bit longer about it, as both package name and version are set within the uploaded package archive, I think we don't really need to ask users to provide the package key in the POST url, as it would be duplicate information.

Open issues

• This PR does not contain changes to the OpenAPI spec file. I'd like to add this endpoint to this spec once it is fully implemented, and the response format has been finalized.

[skh]

@mtojek @ycombinator This might be a good time to have a look at the API endpoint and comment if this works for you or if you would like to see changes.

[ycombinator]

I like it! All the information is (going to) be parsed from package contents so just asking for the package contents in either zip or gzip format makes sense to me. It should also make it very easy to take the artifact produced by elastic-package build and "pipe" it into this API.

👍 👍 from me.

[elasticmachine]

Pinging @elastic/ingest-management (Feature:Fleet)

[kibanamachine]

💚 Build Succeeded

• continuous-integration/kibana-ci/pull-request
• Commit: ad58cdf

Build metrics

page load bundle size

id	value	diff	baseline
ingestManager	468.5KB	+72.0B	468.4KB

History

• 💚 Build #74063 succeeded d8f3203
• 💚 Build #73674 succeeded bad3b65
• 💚 Build #73407 succeeded fab70f2
• 💚 Build #73363 succeeded f921fb9

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[jfsiii]

👍 Thanks for the context/thinking around the routes.