We used to only set it for single-use offers (where it's required),
but it's still interesting for multi-use offers, so let's keep it
there.
We also put this field in the documentation.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Means a reshuffle of our logic: we want to multiply by quantity before
conversion for maximum accuracy.
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>
