Add metadata cli tool UX
Ideas about "MVP" behavior:
- Try to parse a metadata object that's stored in a file (output is probably "list with hash XXX OK/err")
- Try to parse a metadata object that can be located with a URL (output is probably "list with hash XXX OK/err")
- Download a metadata object that can be located with a URL (output is the metadata object if its signature is valid and the content can be parsed).
- Would be nice if it is possible to specify, e.g, "source google" and the tool knows those params
- Probably want to be able to specify urls + pubkey as well
Only output to stdout to keep it simple.
The above should be useful for: linting and authenticated downloads of the list (e.g., by piping to a file).
TODO@later:
- Store metdata object + sig to file
- Check that the downloaded metadata object is consistent with a stored metadata object