All UnknownTransaction fields should be camelCased

[danielcolinjames]

I think we should make UnknownTransactions have all camelCased fields so we can better prepare for when the type is fully supported in helium-js, and avoid re-writing any frontend code (e.g. challenger_owner will eventually have to be updated to challengerOwner)

there are some examples of us doing this with camelCaseKeys() in helium-js

and this may be a separate issue, and I haven't thought it all the way through, but we could probably also convert some or all transactions to automatically return all camelCased keys so that when a new field gets added to hotspot for example, it'll automatically start showing up instead of needing to be manually added to the hotspot definition