fix: add stop method for missing message verifier

waku/v2/api/missing/missing_messages.go

@@ -35,6 +35,7 @@ type MessageTracker interface {
 // MissingMessageVerifier is used to periodically retrieve missing messages from store nodes that have some specific criteria
 type MissingMessageVerifier struct {
 	ctx    context.Context
+	cancel context.CancelFunc
 	params missingMessageVerifierParams
 
 	storenodeRequestor common.StorenodeRequestor
@@ -98,7 +99,9 @@ func (m *MissingMessageVerifier) SetCriteriaInterest(peerID peer.ID, contentFilt
 }
 
 func (m *MissingMessageVerifier) Start(ctx context.Context) {
+	ctx, cancelFunc := context.WithCancel(ctx)
 	m.ctx = ctx
+	m.cancel = cancelFunc
 	m.criteriaInterest = make(map[string]criteriaInterest)
 
 	c := make(chan *protocol.Envelope, 1000)
@@ -141,6 +144,10 @@ func (m *MissingMessageVerifier) Start(ctx context.Context) {
 	}()
 }
 
+func (m *MissingMessageVerifier) Stop() {
+	m.cancel()
+}
+
 func (m *MissingMessageVerifier) fetchHistory(c chan<- *protocol.Envelope, interest criteriaInterest) {
 	contentTopics := interest.contentFilter.ContentTopics.ToList()
 	for i := 0; i < len(contentTopics); i += maxContentTopicsPerRequest {