Copy products, discounts and webhook config between test and live mode

There's no way to copy a catalog from test mode to live. Everything proven in test has to

be recreated by hand in live - products, discounts, webhook endpoint config - and retyping a proven configuration is exactly where a typo enters. ("Clone a product" helps within a mode, but not across them.)

A "copy to live" (and back) would close it. We ended up building our own sync script

against the products API partly for this reason, and it can't carry the license-key

settings because those are dashboard-only.