feat(cooler): Cache.Pull returns and removes a value atomically

- Cache.Pull(ctx, key) ([]byte, bool, error), Laravel's Cache::pull
- Redis driver runs GETDEL (Redis 6.2+); memory driver uses otter Compute
  with InvalidateOp under the per-key lock; expired keys report not found
- TestPullSmoke over the memory driver and miniredis, ExampleCache_Pull
- README and docs/services/caching.md ("One-time values")

modules/cooler/pull_smoke_test.go

@@ -0,0 +1,49 @@
+package cooler
+
+import (
+	"testing"
+	"time"
+)
+
+// TestPullSmoke takes a value exactly once through Pull on both drivers, and
+// reports an expired value as not found.
+func TestPullSmoke(t *testing.T) {
+	run := func(t *testing.T, c Cache, advance func(time.Duration)) {
+		t.Helper()
+		ctx := t.Context()
+
+		if err := c.Set(ctx, "code", []byte("v"), 0); err != nil {
+			t.Fatal(err)
+		}
+		if v, ok, err := c.Pull(ctx, "code"); err != nil || !ok || string(v) != "v" {
+			t.Fatalf("first Pull = %q %v %v, want \"v\" true nil", v, ok, err)
+		}
+		if v, ok, err := c.Pull(ctx, "code"); err != nil || ok || v != nil {
+			t.Fatalf("second Pull = %q %v %v, want nil false nil", v, ok, err)
+		}
+		if v, ok, err := c.Get(ctx, "code"); err != nil || ok || v != nil {
+			t.Fatalf("Get after Pull = %q %v %v, want nil false nil", v, ok, err)
+		}
+
+		if err := c.Set(ctx, "short", []byte("x"), 50*time.Millisecond); err != nil {
+			t.Fatal(err)
+		}
+		advance(100 * time.Millisecond)
+		if v, ok, err := c.Pull(ctx, "short"); err != nil || ok || v != nil {
+			t.Fatalf("Pull of an expired key = %q %v %v, want nil false nil", v, ok, err)
+		}
+	}
+
+	t.Run("memory", func(t *testing.T) {
+		c, err := NewMemoryCache("acme:", 100)
+		if err != nil {
+			t.Fatal(err)
+		}
+		run(t, c, func(time.Duration) { time.Sleep(80 * time.Millisecond) })
+	})
+
+	t.Run("redis", func(t *testing.T) {
+		mr, client := miniClient(t)
+		run(t, NewRedisCache(client, "acme:"), mr.FastForward)
+	})
+}