fix(session): keep cooldown trackers and trim stale chunks by key

Cleanup evicted a refresh tracker by last attempt time alone. A tracker
could leave its cooldown early. Cleanup now also requires the cooldown
to be over.

The stale chunk trim deleted an index range derived from the chunk
count. A sparse key set kept stale high keys and failed the read. The
trim now deletes every key at or above token_total.

refresh_cleanup_chunktrim_test.go

@@ -0,0 +1,49 @@
+package traefikoidc
+
+import (
+	"testing"
+	"time"
+
+	"github.com/gorilla/sessions"
+)
+
+// Cleanup must not evict a tracker whose cooldown is still running.
+func TestRefreshCleanupKeepsTrackerInCooldown(t *testing.T) {
+	cfg := DefaultRefreshCoordinatorConfig()
+	cfg.MaxRefreshAttempts = 2
+	cfg.RefreshAttemptWindow = 20 * time.Millisecond
+	cfg.RefreshCooldownPeriod = time.Hour
+	rc := NewRefreshCoordinator(cfg, GetSingletonNoOpLogger())
+	defer rc.Shutdown()
+
+	rc.recordRefreshAttempt("s")
+	rc.recordRefreshAttempt("s")
+	if !rc.isInCooldown("s") {
+		t.Fatal("precondition: session must enter cooldown")
+	}
+	time.Sleep(80 * time.Millisecond)
+	rc.cleanupStaleEntries()
+	if !rc.isInCooldown("s") {
+		t.Fatal("cleanup evicted a tracker still in cooldown")
+	}
+}
+
+// Stale chunks above token_total must be dropped by key, even when the key
+// set is sparse.
+func TestChunkTrimDropsStaleSparseKeys(t *testing.T) {
+	cm := NewChunkManager(newNoOpLogger())
+	mk := func(s string, total interface{}) *sessions.Session {
+		v := map[interface{}]interface{}{"token_chunk": s}
+		if total != nil {
+			v["token_total"] = total
+		}
+		return &sessions.Session{Values: v}
+	}
+	chunks := map[int]*sessions.Session{
+		0: mk("Zq8xK2mP", 3), 1: mk("r7TnB4wY", nil), 2: mk("c9LdG5sH", nil), 7: mk("stale", nil),
+	}
+	res := cm.processChunkedToken(chunks, RefreshTokenConfig)
+	if res.Error != nil || res.Token != "Zq8xK2mPr7TnB4wYc9LdG5sH" {
+		t.Fatalf("token=%q err=%v, want Zq8xK2mPr7TnB4wYc9LdG5sH", res.Token, res.Error)
+	}
+}