cln-rpc: update schema, update proto for xpay payer_note field

contrib/msggen/msggen/schema.json

@@ -37313,6 +37313,13 @@
               "A payment may be delayed for up to `maxdelay` blocks by another node; clients should be prepared for this worst case."
             ],
             "default": "2016"
+          },
+          "payer_note": {
+            "type": "string",
+            "added": "v26.04",
+            "description": [
+              "A message that a payer is willing to send to a payee within an invoice request."
+            ]
           }
         }
       },
@@ -37399,7 +37406,8 @@
             "id": "example:xpay#2",
             "method": "xpay",
             "params": {
-              "invstring": "lni1qqg0qe03030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303"
+              "invstring": "lni1qqg0qe03030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303",
+              "payer_note": "Coffee payment"
             }
           },
           "response": {