determine if client can use cached version of packages list "available applications"

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Is your feature request related to a problem? Please describe.

This would speed up most requests as the last loaded list is the current one most of the time and also release resources on the server where the public repo is installed.

Describe the solution you'd like

Whenever the list of available packages is queried the server sends a header that will enable to easily determine if that specific listing has changed on subsequent requests.

That could be an eTag or last-modified header.

Describe alternatives you've considered

Leaving it as it is. Every request will rebuild the list of compatible and available packages.

Additional context

This will only have effect when an updated package-service is able to handle responses with status code 304, not modified.