All keys returned for txs containing multiple keys

[rcmorano]

If provided key doesn't match any valid key, graphql returns empty value, but if it does but also contains some other keys, all of them are returned.

Lib should do a) parse keys on client-side and only return the provided one or b) improve graphql query (if that's possible) to only return the matching one.

Another missing feature is that it should be able to default to returning all valid keys when no key is provided.