vault: Track the renew time

vault/expiration.go

@@ -195,6 +195,7 @@ type leaseEntry struct {
 	Data      map[string]interface{}
 	Lease     *Lease
 	IssueTime time.Time
+	RenewTime time.Time
 }
 
 // encode is used to JSON encode the lease entry

vault/expiration_test.go

@@ -77,6 +77,7 @@ func TestLeaseEntry(t *testing.T) {
 			MaxDuration: time.Hour,
 		},
 		IssueTime: time.Now(),
+		RenewTime: time.Now(),
 	}
 
 	enc, err := le.encode()