Added redis backend, backend selection mechanism

backend/null/null.go

@@ -0,0 +1,47 @@
+package backend
+
+import (
+	"context"
+	"errors"
+	"git.thequux.com/thequux/ipasso/backend"
+	"go.uber.org/zap"
+	"net/url"
+)
+
+type NullBackend struct{}
+
+func (n *NullBackend) PutSession(ctx context.Context, session backend.Session, cache backend.SessionCache) error {
+	//TODO implement me
+	zap.L().Info("Put session", zap.Any("session", session), zap.Any("cache", cache))
+	return nil
+}
+
+func (n *NullBackend) GetSession(ctx context.Context, id string) (backend.Session, *backend.SessionCache, error) {
+	//TODO implement me
+	return backend.Session{}, nil, errors.New("no such session")
+}
+
+func (n *NullBackend) EndSession(ctx context.Context, id string) {
+	//TODO implement me
+}
+
+func (n *NullBackend) ReserveSessionID(ctx context.Context, sessionID string) (bool, error) {
+	//TODO implement me
+	return false, nil
+}
+
+func (n *NullBackend) Ping(ctx context.Context) error {
+	//TODO implement me
+	return nil
+}
+
+func (n *NullBackend) DoMaintenance(ctx context.Context) {
+	//TODO implement me
+}
+
+func init() {
+	backend.RegisterBackendFactory("null", "Do-nothing backend. Probably not useful", "Usage: null://",
+		func(*url.URL) (backend.Backend, error) {
+			return &NullBackend{}, nil
+		})
+}