Refactor finality relay helpers (#1220)

* refactor finality relay helper definitions

* add missing doc

* removed commented code

* fmt

* disable rustfmt for macro

* move best_finalized method const to relay chain def

bridges/relays/client-substrate/src/chain.rs

@@ -32,6 +32,13 @@ use std::{fmt::Debug, time::Duration};
 pub trait Chain: ChainBase + Clone {
 	/// Chain name.
 	const NAME: &'static str;
+	/// Name of the runtime API method that is returning best known finalized header number
+	/// and hash (as tuple).
+	///
+	/// Keep in mind that this method is normally provided by the other chain, which is
+	/// bridged with this chain.
+	const BEST_FINALIZED_HEADER_ID_METHOD: &'static str;
+
 	/// Average block interval.
 	///
 	/// How often blocks are produced on that chain. It's suggested to set this value
@@ -45,7 +52,7 @@ pub trait Chain: ChainBase + Clone {
 	/// Block type.
 	type SignedBlock: Member + Serialize + DeserializeOwned + BlockWithJustification<Self::Header>;
 	/// The aggregated `Call` type.
-	type Call: Clone + Dispatchable + Debug;
+	type Call: Clone + Dispatchable + Debug + Send;
 
 	/// Type that is used by the chain, to convert from weight to fee.
 	type WeightToFee: WeightToFeePolynomial<Balance = Self::Balance>;
@@ -102,6 +109,9 @@ impl<C: Chain> UnsignedTransaction<C> {
 	}
 }
 
+/// Account key pair used by transactions signing scheme.
+pub type AccountKeyPairOf<S> = <S as TransactionSignScheme>::AccountKeyPair;
+
 /// Substrate-based chain transactions signing scheme.
 pub trait TransactionSignScheme {
 	/// Chain that this scheme is to be used.