Study if some repositories can be static

In Qt Installer, we have a lot of repositories in Archive category that never changes. If the Archive category meta items are already cached, there should be no need to evaluate if those have updates or not as we know they don't have.
Suggestion - add possibility to mark some repositories static so that installer will know that the metadata can be used from cache directly without checking if there are updates. At the same time we could make the interface more generic if there occurs other demands in the future - like "no" when we do not ever cache the repository.
for example:

{ "action": "add", "cache": "no/yes/static/etc." "categories": [ "Archive" ], "name": "My Old Repository", "releasedate": "2020-11-20T11:00:00.000Z", "url": "https://repository_address" }

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