Migrated from: https://wikimedia.mingle.thoughtworks.com/projects/multimedia/cards/294
Narrative
As a wiki administrator, I can filter out maintenance thumbnails so that readers are not annoyed by them.
When clicking on thumbnails or using prev/next, non-content images such as problem template icons should be excluded from MediaViewer.
#229 fixed this issue for enwiki, but other wikis might have different syntax, and local admins should be able to fix this for their wiki.
Acceptance Criteria
- There is an easy way (defining a function with a given name, subscribing to an event etc) for wiki admins to block certain images from appearing in MediaViewer.