Alternate way for optional parameters in v6?

[iamPiyushNagpal]

In v5, we could add trailing ? to route for optional parameters, but as in v6, the support for the same has been dropped, so what's the alternate way of writing the following piece of code?

<Route path="/cart/:id?" component={<CartPage />} />

[brophdawg11]

Superseded by #9546