Centralize Ticket management of persistent stores (#682)

* Centralize Ticket management of persistent stores

persistence package with Manager & Ticket will handle
all the details about keys, secrets, ticket into cookies,
etc. Persistent stores just need to pass Save, Load &
Clear function handles to the persistent manager now.

* Shift to persistence.Manager wrapping a persistence.Store

* Break up the Redis client builder logic

* Move error messages to Store from Manager

* Convert ticket to private for Manager use only

* Add persistence Manager & ticket tests

* Make a custom MockStore that handles time FastForwards

pkg/sessions/persistence/manager_test.go

@@ -0,0 +1,34 @@
+package persistence
+
+import (
+	"testing"
+	"time"
+
+	"github.com/oauth2-proxy/oauth2-proxy/pkg/apis/options"
+	sessionsapi "github.com/oauth2-proxy/oauth2-proxy/pkg/apis/sessions"
+	"github.com/oauth2-proxy/oauth2-proxy/pkg/logger"
+	"github.com/oauth2-proxy/oauth2-proxy/pkg/sessions/tests"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+)
+
+func TestManager(t *testing.T) {
+	logger.SetOutput(GinkgoWriter)
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "Persistence Manager SessionStore")
+}
+
+var _ = Describe("Persistence Manager SessionStore Tests", func() {
+	var ms *tests.MockStore
+	BeforeEach(func() {
+		ms = tests.NewMockStore()
+	})
+	tests.RunSessionStoreTests(
+		func(_ *options.SessionOptions, cookieOpts *options.Cookie) (sessionsapi.SessionStore, error) {
+			return NewManager(ms, cookieOpts), nil
+		},
+		func(d time.Duration) error {
+			ms.FastForward(d)
+			return nil
+		})
+})