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/tests/mock_store.go

@@ -0,0 +1,58 @@
+package tests
+
+import (
+	"context"
+	"fmt"
+	"time"
+)
+
+// entry is a MockStore cache entry with an expiration
+type entry struct {
+	data       []byte
+	expiration time.Duration
+}
+
+// MockStore is a generic in-memory implementation of persistence.Store
+// for mocking in tests
+type MockStore struct {
+	cache   map[string]entry
+	elapsed time.Duration
+}
+
+// NewMockStore creates a MockStore
+func NewMockStore() *MockStore {
+	return &MockStore{
+		cache:   map[string]entry{},
+		elapsed: 0 * time.Second,
+	}
+}
+
+// Save sets a key to the data to the memory cache
+func (s *MockStore) Save(_ context.Context, key string, value []byte, exp time.Duration) error {
+	s.cache[key] = entry{
+		data:       value,
+		expiration: exp,
+	}
+	return nil
+}
+
+// Load gets data from the memory cache via a key
+func (s *MockStore) Load(_ context.Context, key string) ([]byte, error) {
+	entry, ok := s.cache[key]
+	if !ok || entry.expiration <= s.elapsed {
+		delete(s.cache, key)
+		return nil, fmt.Errorf("key not found: %s", key)
+	}
+	return entry.data, nil
+}
+
+// Clear deletes an entry from the memory cache
+func (s *MockStore) Clear(_ context.Context, key string) error {
+	delete(s.cache, key)
+	return nil
+}
+
+// FastForward simulates the flow of time to test expirations
+func (s *MockStore) FastForward(duration time.Duration) {
+	s.elapsed += duration
+}

pkg/sessions/tests/session_store_tests.go

@@ -133,18 +133,6 @@ func RunSessionStoreTests(newSS NewSessionStoreFunc, persistentFastForward Persi
 				PersistentSessionStoreInterfaceTests(&input)
 			}
 		})
-
-		Context("with an invalid cookie secret", func() {
-			BeforeEach(func() {
-				input.cookieOpts.Secret = "invalid"
-			})
-
-			It("returns an error when initialising the session store", func() {
-				ss, err := newSS(opts, input.cookieOpts)
-				Expect(err).To(MatchError("error initialising cipher: crypto/aes: invalid key size 7"))
-				Expect(ss).To(BeNil())
-			})
-		})
 	})
 }