Internal app sharing lets you upload a file, and get a URL in return. Authorised users can open the URL on their device, which takes them to Google Play to install the app directly (if they've enabled internal apps).

APKs and Bundles can be uploaded directly, without having to create an edit session — you just need the Application ID and the file itself:
https://developers.google.com/android-publisher/api-ref/internalappsharingartifacts/uploadapk

The question is how should this be implemented in the plugin?

I think it should be a special track name in the existing `androidApkUpload` step, e.g. `internal-app-sharing`.

Although the underlying implementation will be a little different, we still want to have the basics like a credential, file pattern, and the track name. We'll want to examine the file to check it's valid, and display some metadata before uploading.

We need to display the download URL once the upload has been accepted.

It would be very useful to also store this as build metadata, so the URL can be retrieved via the Jenkins API. This relates to JENKINS-32107, i.e. it would be nice to implement the metadata storage in a way that's generic, rather than specific to uploading internal sharing artifacts.