This avoids a footgun where they create an offer then we can't create
the invoice because they don't have a converter plugin.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
We split `send_invoice` offers inoo offerout (for want of a better name).
This simplifies the API.
Also took the opportunity to move the `vendor` tag to immediately
follow `description` (our tests use arguments by keywords, so no
change there).
Suggested-by: shesek
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
refund offers are implied send_invoice offers. And send_invoice offers
are implied single-use offers, though it can also make sense to have
a non-send_invoice offer be single-use.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Rusty Russell