Add equivocation detector crate and implement clients (#2348) (#2353)

* Split FinalitySyncPipeline and SourceClient

* Move some logic to finality_base

* Add empty equivocation detection clients

* Add equivocation reporting logic to the source client

* Use convenience trait for SubstrateFinalitySyncPipeline

* Define JustificationVerificationContext for GRANDPA

* Equivocation source client: finality_verification_context()

* Equivocation source client: synced_headers_finality_info()

* reuse HeaderFinalityInfo

* Define EquivocationsFinder

* Fix spellcheck

* Address review comments

* Avoid equivocations lookup errors

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

@@ -16,16 +16,17 @@
 
 use crate::calls::UtilityCall;
 
-use bp_header_chain::UnderlyingChainWithGrandpaProvider;
+use bp_header_chain::ChainWithGrandpa as ChainWithGrandpaBase;
 use bp_messages::MessageNonce;
 use bp_runtime::{
 	Chain as ChainBase, ChainId, EncodedOrDecodedCall, HashOf, Parachain as ParachainBase,
 	TransactionEra, TransactionEraOf, UnderlyingChainProvider,
 };
-use codec::{Codec, Encode};
+use codec::{Codec, Decode, Encode};
 use jsonrpsee::core::{DeserializeOwned, Serialize};
 use num_traits::Zero;
 use sc_transaction_pool_api::TransactionStatus;
+use scale_info::TypeInfo;
 use sp_core::{storage::StorageKey, Pair};
 use sp_runtime::{
 	generic::SignedBlock,
@@ -78,7 +79,7 @@ pub trait RelayChain: Chain {
 ///
 /// Keep in mind that parachains are relying on relay chain GRANDPA, so they should not implement
 /// this trait.
-pub trait ChainWithGrandpa: Chain + UnderlyingChainWithGrandpaProvider {
+pub trait ChainWithGrandpa: Chain + ChainWithGrandpaBase {
 	/// Name of the runtime API method that is returning the GRANDPA info associated with the
 	/// headers accepted by the `submit_finality_proofs` extrinsic in the queried block.
 	///
@@ -87,7 +88,7 @@ pub trait ChainWithGrandpa: Chain + UnderlyingChainWithGrandpaProvider {
 	const SYNCED_HEADERS_GRANDPA_INFO_METHOD: &'static str;
 
 	/// The type of the key owner proof used by the grandpa engine.
-	type KeyOwnerProof;
+	type KeyOwnerProof: Decode + TypeInfo + Send;
 }
 
 /// Substrate-based parachain from minimal relay-client point of view.

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

@@ -22,8 +22,8 @@ use crate::{
 		SubstrateAuthorClient, SubstrateChainClient, SubstrateFinalityClient,
 		SubstrateFrameSystemClient, SubstrateStateClient, SubstrateSystemClient,
 	},
-	transaction_stall_timeout, AccountKeyPairOf, ConnectionParams, Error, HashOf, HeaderIdOf,
-	Result, SignParam, TransactionTracker, UnsignedTransaction,
+	transaction_stall_timeout, AccountKeyPairOf, ChainWithGrandpa, ConnectionParams, Error, HashOf,
+	HeaderIdOf, Result, SignParam, TransactionTracker, UnsignedTransaction,
 };
 
 use async_std::sync::{Arc, Mutex, RwLock};
@@ -715,15 +715,16 @@ impl<C: Chain> Client<C> {
 		Ok(Subscription(Mutex::new(receiver)))
 	}
 
-	// TODO: remove warning after implementing
-	// https://github.com/paritytech/parity-bridges-common/issues/39
-	#[allow(dead_code)]
-	async fn generate_grandpa_key_ownership_proof(
+	/// Generates a proof of key ownership for the given authority in the given set.
+	pub async fn generate_grandpa_key_ownership_proof(
 		&self,
 		at: HashOf<C>,
 		set_id: sp_consensus_grandpa::SetId,
 		authority_id: sp_consensus_grandpa::AuthorityId,
-	) -> Result<Option<sp_consensus_grandpa::OpaqueKeyOwnershipProof>> {
+	) -> Result<Option<sp_consensus_grandpa::OpaqueKeyOwnershipProof>>
+	where
+		C: ChainWithGrandpa,
+	{
 		self.typed_state_call(
 			SUB_API_GRANDPA_GENERATE_KEY_OWNERSHIP_PROOF.into(),
 			(set_id, authority_id),