Feature to mark apps as deprecated

[ocdtrekkie]

The app market should have a way to mark an app as deprecated. Ideally, the holder of the packaging key should be able to deprecate an app from the spk publish command, and the app index admins should also be able to mark an app as deprecated.

A deprecated app should probably not be visible in the app market, if browsing it, but should be visible from it's exact app page link. A ?deprecated=true flag to view deprecated apps would also be a very nice thing to have.

The primary purpose for this would be to "hide" apps that are significantly broken and unsupported, or have been supplanted/replaced my newer non-compatible packages. If FooApp1 can't be upgraded to FooApp2, and we don't want new users to install FooApp1, we should hide it from the market. However, the app index still should respond for it if people need to reinstall the app when restoring an old grain or performing a mass transfer. Even if, for example, we completely break Roundcube's mail handling and hence, should not advertise it to new users, we need to retain the ability for an existing user to reinstall it from the app market to get their data from it.

[ocdtrekkie]

I'm pondering having a PR-updated list for this or something that would be quicker to implement, since we should not dedicate much/any effort into this particular app market, I think, and this should happen similarly infrequently to key replacements.

Currently I'd like to hide from the app list:

CodiMD
SandMD
MediaWiki (2016 version)

But still allow the pages to load if you navigated to them directly.

I am tempted to look into attempting this myself at some point though I am mildly afraid of what building the app market might entail.