Chain Selection: Follow-ups (#3328)

* DB skeleton

* key formats

* lexicographic test

* custom types for DB

* implement backend for db-v1

* remove VoidBackend and integrate with real DbBackend

* detect stagnant blocks on in interval

* fix tests

* add tests for stagnant

* send ChainSelectionMessage::Approved

* tests for DB backend

* unused import

* upgrade kvdb-memorydb

Co-authored-by: Andronik Ordian <write@reusable.software>

polkadot/node/core/approval-voting/src/lib.rs

@@ -26,7 +26,7 @@ use polkadot_node_subsystem::{
 		AssignmentCheckError, AssignmentCheckResult, ApprovalCheckError, ApprovalCheckResult,
 		ApprovalVotingMessage, RuntimeApiMessage, RuntimeApiRequest, ChainApiMessage,
 		ApprovalDistributionMessage, CandidateValidationMessage,
-		AvailabilityRecoveryMessage,
+		AvailabilityRecoveryMessage, ChainSelectionMessage,
 	},
 	errors::RecoveryError,
 	Subsystem, SubsystemContext, SubsystemError, SubsystemResult, SpawnedSubsystem,
@@ -717,6 +717,7 @@ enum Action {
 		candidate: CandidateReceipt,
 		backing_group: GroupIndex,
 	},
+	NoteApprovedInChainSelection(Hash),
 	IssueApproval(CandidateHash, ApprovalVoteRequest),
 	BecomeActive,
 	Conclude,
@@ -962,6 +963,9 @@ async fn handle_actions(
 					Some(_) => {},
 				}
 			}
+			Action::NoteApprovedInChainSelection(block_hash) => {
+				ctx.send_message(ChainSelectionMessage::Approved(block_hash).into()).await;
+			}
 			Action::BecomeActive => {
 				*mode = Mode::Active;
 
@@ -1805,6 +1809,7 @@ fn import_checked_approval(
 
 			if is_block_approved && !was_block_approved {
 				metrics.on_block_approved(status.tranche_now as _);
+				actions.push(Action::NoteApprovedInChainSelection(block_hash));
 			}
 
 			actions.push(Action::WriteBlockEntry(block_entry));