Background

As a first step towards fulfilling T191027, we should disable editing the article description if we detect that the description came from the local article instead of Wikidata. This will be a stopgap measure to avoid confusion for users who might edit the description (using our current workflow, which sends the edit to Wikidata), but then notice that their edit isn't being reflected in the article.

This will depend on the Page Content Service implementing the descriptionsource parameter in the mobile-sections-lead endpoint, similarly to how it's currently implemented in the MW API as part of the prop=description request.

Steps to QA

SCENARIO A. View and edit an article with a description that is locally sourced

Note: An article is using a locally-sourced title description (instead of from wikidata) when the template {{short description}} is in the lead section of the article (visible in wikitext edit mode).

1. Open an article using a locally-sourced title description, e.g., Wagon Train
2. Tap on the edit pencil icon in the lead section of the article. It is expected this will open the view to edit the lead section of the article, which contains the {{short description}} template.
3. Edit the short description (suggest a minor grammatical corrections, such as Western television series that aired 1957-1965)
4. Complete preview and publish of the minor edit. It is expected that the title description should be updated

SCENARIO B. Edit an article with no title description, then override with locally-sourced description

1. Find an article on EN.wiki which does not yet contain a title description. To help find articles, try inputing a generic search term (e.g., Cake, station, esplanade, creek) and selecting a search result which does not yet have a description. For example, open "Madeira cake"). It is expected the article will contain an action to "Add title description".
2. Tap to add a title description, for e.g. type of cake, and tap the checkmark on the top right of the toolbar to publish. It is expected the article will refresh with the title description updated to the text entered in the previous step.
3. Tap on the first edit pencil. It is expected that a menu will appear with an option to "Edit title description" and "Edit introduction".
4. Select "Edit introduction" and add the '{{short description}} template to override the title description with a local description. For example, add to the very top of the Madeira cake article introduction: {{ short description|type of sponge cake}} and proceed to finish publishing. It is expected that the title description under the article title will now show this new locally sourced description.
5. Once again, tap on the first edit pencil icon on the article. It is expected that this will now immediately open the article to editing the introduction section.
6. Remove the {{short description}] added in step 4 and publish the edit. It is expected the article's title description will revert to using the description entered in step 2 (from wikidata).