Add SessionStore interface

pkg/apis/sessions/interfaces.go

@@ -0,0 +1,12 @@
+package sessions
+
+import (
+	"net/http"
+)
+
+// SessionStore is an interface to storing user sessions in the proxy
+type SessionStore interface {
+	SaveSession(rw http.ResponseWriter, req *http.Request, s *SessionState) error
+	LoadSession(req *http.Request) (*SessionState, error)
+	ClearSession(rw http.ResponseWriter, req *http.Request) error
+}