lnrpc: add maxFeeRatio to FundPsbtRequest

lnrpc/walletrpc/walletkit.swagger.json

@@ -1589,6 +1589,11 @@
         "coin_selection_strategy": {
           "$ref": "#/definitions/lnrpcCoinSelectionStrategy",
           "description": "The strategy to use for selecting coins during funding the PSBT."
+        },
+        "max_fee_ratio": {
+          "type": "number",
+          "format": "double",
+          "description": "The max fee to total output amount ratio that this psbt should adhere to."
         }
       }
     },