persist middleware trong Zustand hoạt động như thế nào?

const useAuthStore = create(
  persist(
    (set) => ({ user: null, theme: 'light', loading: false }),
    {
      name: 'auth-storage',
      partialize: (s) => ({ user: s.user, theme: s.theme }),
      storage: createJSONStorage(() => sessionStorage),
      version: 2,
      migrate: (persistedState, version) =>
        version === 1 ? { ...persistedState, newField: 'default' } : persistedState,
      onRehydrateStorage: () => (state, error) => {
        if (error) console.error('hydration failed', error)
      },
    },
  ),
)