Just a thought about a feature that I've wanted on several occasions. It would be neat if MediaWiki extensions could include wiki content, such as templates which are copied into the wiki and can be overridden there. A similar mechanism might be helpful for local development, where the extension provides some of the custom content that it's responsible for managing, for example E:CentralNotice might install a few fully functional, example campaigns and banners into the database. Thanks for doing this important work!
Topic on Talk:Developer Satisfaction Survey/2019
This is a great idea. It might not be good to do it automatically, howecver, perhaps we could make a small tool which imports example content from the extension source directory in a standardized location and format.
I see what you mean and agree that sample data shouldn't be automatically installed. A CLI tool makes sense for loading, and maybe we can also expose a checkbox for sample data when installing the extension from the MediaWiki installer.
There still might be a second type of content which would be more automatic-install-aligned such as default templates, but it's just something to keep in mind at this point.