And document the partid arg.
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSON-RPC: `sendonion` has a new optional `bolt11` argument for when it's used to pay an invoice.
Te `sendonion` docs where claiming that the `first_hop` needs to specify a
`channel_id` whereas it should really be the `node_id` of the peer we are
trying to contact.
Changelog-Added: Added `createonion` and `sendonion` JSON-RPC methods allowing the implementation of custom protocol extensions that are not directly implemented in c-lightning itself.