feat(npm): add backend to fetch data from private registries

[christoph-jerolimov]

Hey, I just made a Pull Request!

• This PR adds a new backend plugin to fetch npm packages from custom registries or from npmjs.com with an auth token.
• For that I moved the fetch code into a common package. Incl. the annotations and some utils like isNpmPackage
• Updated the readme and added some techdocs to the plugin. Fyi: I linked the README and docs from the plugins so that we have just one source in the root of the workspace.

The included backstage app contains catalog examples for npmjs and GitHub. Also if the GitHub example is public, it requires an authtoken and an app-config.local.yaml like this:

npm:
  defaultRegistry: npmjs
  registries:
    - name: npmjs
      url: https://registry.npmjs.com
    - name: github
      url: https://npm.pkg.github.com
      token: ghp_....

Catalog entities can reference this registries with a new annotation:

apiVersion: backstage.io/v1alpha1
kind: Component
metadata:
  name: github-packages-examples
  annotations:
    npm/registry: github
    npm/package: '@github-packages-examples/npm-publish'
...

The GitHub example looks then like this:

http://localhost:3000/catalog/default/component/github-packages-examples

The local backstage incl. a catalog entity for the tech docs:

http://localhost:3000/docs/default/component/backstage-plugin-npm

✔️ Checklist

• A changeset describing the change and affected packages. (more info)
• Added or updated documentation
• Tests for new functionality and regression tests for bug fixes
• Screenshots attached (for UI changes)
• All your commits have a Signed-off-by line in the message. (more info)

[backstage-goalie]

Thanks for the contribution!
All commits need to be DCO signed before they are reviewed. Please refer to the the DCO section in CONTRIBUTING.md or the DCO status for more info.

[backstage-goalie]

Changed Packages

Package Name	Package Path	Changeset Bump	Current Version
app-next	workspaces/npm/packages/app-next	none	v0.0.0
backend	workspaces/npm/packages/backend	none	v0.0.0
@backstage-community/plugin-npm-backend	workspaces/npm/plugins/npm-backend	minor	v1.1.0
@backstage-community/plugin-npm-common	workspaces/npm/plugins/npm-common	minor	v1.1.0
@backstage-community/plugin-npm	workspaces/npm/plugins/npm	minor	v1.1.0

[github-actions]

This PR has been automatically marked as stale because it has not had recent activity from the author. It will be closed if no further activity occurs. If the PR was closed and you want it re-opened, let us know and we'll re-open the PR so that you can continue the contribution!

[christoph-jerolimov]

@karthikjeeyar @awanlin I finally got the backend plugin into a state where I'm mostly happy. And kind of feedback is very welcome. :)

[awanlin]

This looks good to me @christoph-jerolimov, as mentioned previously let's try out the pattern you've got for the README files and see how it works once published to NPM.

Going to approve but leave the merging to you. 👍

[christoph-jerolimov]

@awanlin it didn't worked. 😞

https://github.com/backstage/community-plugins/actions/runs/12773015777/job/35604234982

Sorry that I didn't tried yarn pack... I will take care of that later with a follow-up PR.

[awanlin]

No worries, I think it was good that we gave this a try and now we know it won't work. 👍