Add first unit test for authApplierV3

This contains a slight refactoring to expose enough information
to write meaningful tests for auth applier v3.

Signed-off-by: Thomas Jungblut <tjungblu@redhat.com>

server/lease/lessor.go

@@ -281,12 +281,7 @@ func (le *lessor) Grant(id LeaseID, ttl int64) (*Lease, error) {
 
 	// TODO: when lessor is under high load, it should give out lease
 	// with longer TTL to reduce renew load.
-	l := &Lease{
-		ID:      id,
-		ttl:     ttl,
-		itemSet: make(map[LeaseItem]struct{}),
-		revokec: make(chan struct{}),
-	}
+	l := NewLease(id, ttl)
 
 	le.mu.Lock()
 	defer le.mu.Unlock()
@@ -838,6 +833,15 @@ type Lease struct {
 	revokec chan struct{}
 }
 
+func NewLease(id LeaseID, ttl int64) *Lease {
+	return &Lease{
+		ID:      id,
+		ttl:     ttl,
+		itemSet: make(map[LeaseItem]struct{}),
+		revokec: make(chan struct{}),
+	}
+}
+
 func (l *Lease) expired() bool {
 	return l.Remaining() <= 0
 }
@@ -861,6 +865,13 @@ func (l *Lease) TTL() int64 {
 	return l.ttl
 }
 
+// SetLeaseItem sets the given lease item, this func is thread-safe
+func (l *Lease) SetLeaseItem(item LeaseItem) {
+	l.mu.Lock()
+	defer l.mu.Unlock()
+	l.itemSet[item] = struct{}{}
+}
+
 // RemainingTTL returns the last checkpointed remaining TTL of the lease.
 // TODO(jpbetz): do not expose this utility method
 func (l *Lease) RemainingTTL() int64 {