Storing multiple Justifications per block (#7640)

* primitives/runtime: initial changes on supporting multiple Justifications

* primitives/runtime: make Justifications strongly typed

* Encode/decode Justifications

* primitives/runtime: add Justification type

* backend: apply_finality and finalize_block takes a single Justification

* manual-seal: create engine id and let rpc take encoded justification

* backend: skeleton functions for appending justifications

* backend: initial implementation append_justification

Initial implementation of append_justification on the Backend trait, and also remove unused skeleton
functions for append_justificaton on Finaziler trait.
k

* backend: guard against duplicate consensus engine id

* client/db: add check for block finality

* client/api: add append_justification to in_mem db

* client/light: add no-op append_justification

* network: fix decode call for Justification

* network: only send a single Justification in BlockData

* network: minor comment update

* protocol: update field names to distinguish single justification

* client: further field renames to plural

* client: update function names to plural justifications

* client/db: upgrade existing database for new format

* network: remove dependency on grandpa crate

* db: fix check for finalized block

* grandpa: check for multiple grandpa justifications hwne importing

* backend: update Finalizer trait to take multiple Justifications

* db: remove debugging statements in migration code

* manual-seal: update note about engine id

* db: fix check for finalized block

* client: update variable name to reflect it is now plural

* grandpa: fix incorrect empty Justications in test

* primitives: make Justifications opaque to avoid being empty

* network: fix detecting empty Justification

* runtime: doc strings for Justifications functions

* runtime: add into_justifications

* primitives: check for duplicates in when adding to Justifications

* network/test: use real grandpa engine id in test

* client: fix reviewer comments

* primitives: rename Justifications::push to append

* backend: revert changes to Finalizer trait

* backend: revert mark_finalized

* backend: revert changes to finalize_block

* backend: revert finalized_blocks

* db: add a quick early return for performance

* client: minor reviewer comments

* service/test: use local ConsensusEngineId

* network: add link to issue for sending multiple Justifications

* Apply suggestions from code review

Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>

* Apply suggestions from code review

Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>

* network: tweaks to review suggestions

* network: revert change to BlockData for backwards compatibility

* Apply suggestion from code review

Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>

* Apply suggestions from code review

Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>

* primitives: update doc comment for Justifications

* client/db/upgrade: avoid grandpa crate dependency

* consensus: revert to single Justification for import_justification

* primitives: improve justifications docs

* style cleanups

* use and_then

* client: rename JUSTIFICATIONS db column

* network: revert to using FRNK in network-test

Co-authored-by: Pierre Krieger <pierre.krieger1708@gmail.com>
Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>
Co-authored-by: André Silva <andrerfosilva@gmail.com>

substrate/client/consensus/manual-seal/src/rpc.rs

@@ -28,7 +28,7 @@ use futures::{
 	SinkExt
 };
 use serde::{Deserialize, Serialize};
-use sp_runtime::Justification;
+use sp_runtime::EncodedJustification;
 pub use self::gen_client::Client as ManualSealClient;
 
 /// Future's type for jsonrpc
@@ -62,7 +62,7 @@ pub enum EngineCommand<Hash> {
 		/// sender to report errors/success to the rpc.
 		sender: Sender<()>,
 		/// finalization justification
-		justification: Option<Justification>,
+		justification: Option<EncodedJustification>,
 	}
 }
 
@@ -83,7 +83,7 @@ pub trait ManualSealApi<Hash> {
 	fn finalize_block(
 		&self,
 		hash: Hash,
-		justification: Option<Justification>
+		justification: Option<EncodedJustification>
 	) -> FutureResult<bool>;
 }
 
@@ -131,7 +131,7 @@ impl<Hash: Send + 'static> ManualSealApi<Hash> for ManualSeal<Hash> {
 		Box::new(future.map_err(Error::from).compat())
 	}
 
-	fn finalize_block(&self, hash: Hash, justification: Option<Justification>) -> FutureResult<bool> {
+	fn finalize_block(&self, hash: Hash, justification: Option<EncodedJustification>) -> FutureResult<bool> {
 		let mut sink = self.import_block_channel.clone();
 		let future = async move {
 			let (sender, receiver) = oneshot::channel();