Add events to the existing [[https://meta.wikimedia.org/wiki/Schema:MobileWikiAppEdit | MobileWikiAppEdit schema]] at least for the following four steps:
- The editor is launched, either (in case the article already has a Wikidata description) selected from the "Edit title description" / "edit introduction" popup menu , or by tapping on the "Add short description link" if the article does not have a description: use the existing `start`action
- The editor is ready (cursor blinking): add a new `ready`action
- The save button is tapped: use the existing `saveAttempt` action
- The edit is saved successfully: add a new `saved`action
Also, all these should indicate whether a new description is being added or an existing description is being updated, via a new `WikidataDescriptionEdit` field with values `new` and `existing`, and `required = false`.
Once there is a path from the editing screen to logging in (T154785) /creating an account, we should also augment the `source` field in the [[https://meta.wikimedia.org/wiki/Schema:MobileWikiAppLogin |MobileWikiAppLogin ]] and [[https://meta.wikimedia.org/wiki/Schema:MobileWikiAppCreateAccount |MobileWikiAppCreateAccount]] schemas with an `WikidataDescriptionEdit` value.