CandidateBackingSubsystem (#1312)

* Updates guide for CandidateBacking

* Move assignment types to primitives

* Initial implementation.

* More functionality

* use assert_matches

* Changes to report misbehaviors

* Some fixes after a review

* Remove a blank line

* Update guide and some types

* Adds run_job function

* Some comments and refactorings

* Fix review

* Remove warnings

* Use summary in kicking off validation

* Parallelize requests

* Validation provides local and global validation params

* Test issued validity tracking

* Nits from review

polkadot/statement-table/src/generic.rs

@@ -28,6 +28,8 @@ use std::collections::hash_map::{HashMap, Entry};
 use std::hash::Hash;
 use std::fmt::Debug;
 
+use primitives::parachain::{ValidityAttestation as PrimitiveValidityAttestation, ValidatorSignature};
+
 use codec::{Encode, Decode};
 
 /// Context for the statement table.
@@ -98,7 +100,7 @@ pub enum ValidityDoubleVote<C, D, S> {
 	/// Implicit vote by issuing and explicitly voting invalidity
 	IssuedAndInvalidity((C, S), (D, S)),
 	/// Direct votes for validity and invalidity
-	ValidityAndInvalidity(D, S, S),
+	ValidityAndInvalidity(C, S, S),
 }
 
 /// Misbehavior: multiple signatures on same statement.
@@ -180,6 +182,15 @@ pub enum ValidityAttestation<S> {
 	Explicit(S),
 }
 
+impl Into<PrimitiveValidityAttestation> for ValidityAttestation<ValidatorSignature> {
+	fn into(self) -> PrimitiveValidityAttestation {
+		match self {
+			Self::Implicit(s) => PrimitiveValidityAttestation::Implicit(s),
+			Self::Explicit(s) => PrimitiveValidityAttestation::Explicit(s),
+		}
+	}
+}
+
 /// An attested-to candidate.
 #[derive(Clone, PartialEq, Decode, Encode)]
 pub struct AttestedCandidate<Group, Candidate, AuthorityId, Signature> {
@@ -550,7 +561,7 @@ impl<C: Context> Table<C> {
 						// valid vote conflicting with invalid vote
 						(ValidityVote::Valid(good), ValidityVote::Invalid(bad)) |
 						(ValidityVote::Invalid(bad), ValidityVote::Valid(good)) =>
-							make_vdv(ValidityDoubleVote::ValidityAndInvalidity(digest, good, bad)),
+							make_vdv(ValidityDoubleVote::ValidityAndInvalidity(votes.candidate.clone(), good, bad)),
 
 						// two signatures on same candidate
 						(ValidityVote::Issued(a), ValidityVote::Issued(b)) =>
@@ -817,7 +828,7 @@ mod tests {
 		assert_eq!(
 			table.detected_misbehavior.get(&AuthorityId(2)).unwrap(),
 			&Misbehavior::ValidityDoubleVote(ValidityDoubleVote::ValidityAndInvalidity(
-				candidate_digest,
+				Candidate(2, 100),
 				Signature(2),
 				Signature(2),
 			))