* Add a Node Role RPC call
* Formatting
* Fix tests
* Change tests to use NodeRole::Authority so I don't forget to update the test
* Improve role checking
* return a vec instead
* fix tests
* Extract author API from the substrate-rpc crate.
* Split out API from RPC.
* Clean up naming.
* Fix tests.
* Shorten error translations.
* Update Cargo.lock