offers: correctly advertize MPP in invoice features.

Turns out we weren't wiring them through!  And libplugin wasn't reading them anyway.

Changelog-Fixed: lightningd: tell plugins our bolt12 features (so our bolt12 invoices explicitly allow MPP).
Signed-off-by: Rusty Russell <[email protected]>

Author: rustyrussell

common/features.c

@@ -24,7 +24,10 @@ const char *feature_place_names[] = {
 	NULL,
 	"node",
 	"channel",
-	"invoice"
+	"invoice",
+	"bolt12_offer",
+	"bolt12_invreq",
+	"bolt12_invoice",
 };
 
 static const struct feature_style feature_styles[] = {

plugins/libplugin.c

@@ -1475,6 +1475,12 @@ static struct feature_set *json_to_feature_set(struct plugin *plugin,
 			p = CHANNEL_FEATURE;
 		else if (json_tok_streq(buf, t, "invoice"))
 			p = BOLT11_FEATURE;
+		else if (json_tok_streq(buf, t, "bolt12_offer"))
+			p = BOLT12_OFFER_FEATURE;
+		else if (json_tok_streq(buf, t, "bolt12_invreq"))
+			p = BOLT12_INVREQ_FEATURE;
+		else if (json_tok_streq(buf, t, "bolt12_invoice"))
+			p = BOLT12_INVOICE_FEATURE;
 		else
 			continue;
 		fset->bits[p] = json_tok_bin_from_hex(fset, buf, t + 1);