Support tokenization

[peterwilsoncc]

The dummy gateway currently lists a number of subscription features as supported but does not indicate support for tokenization.

As tokenization is more flexible than the subscriptions features, it would be good to add support for the feature to the dummy gateway to allow for testing of automated payments that are not tied to WooCommerce Subscriptions.

This will assist with https://github.com/woocommerce/woocommerce-deposits/issues/375

I can look in to providing a PR for this.

[PanosSynetos]

Hey hey Peter @peterwilsoncc ! Thanks for this and offering to provide a PR. Please go ahead with the PR, it seems like a great addition.

[peterwilsoncc]

FYI, I'll be working on this piecemeal as I work on the Deposits issue. I'll only mark the associated PR ready once that's complete so I can be sure I haven't missed anything.

[PanosSynetos]

Thanks @peterwilsoncc - Make sure to assign @woocommerce/somewherewarm as the reviewer, if you need an additional pair of eyes.