lnd+lnrpc: add msat forwarding amount fields to ForwardingHistory

lnrpc/rpc.proto

@@ -2498,6 +2498,13 @@ message ForwardingEvent {
     /// The total fee (in milli-satoshis) that this payment circuit carried.
     uint64 fee_msat = 8 [json_name = "fee_msat"];
 
+    /// The total amount (in milli-satoshis) of the incoming HTLC that created half the circuit.
+    uint64 amt_in_msat = 9 [json_name = "amt_in_msat"];
+
+    /// The total amount (in milli-satoshis) of the outgoing HTLC that created the second half of the circuit.
+    uint64 amt_out_msat = 10 [json_name = "amt_out_msat"];
+
+
     // TODO(roasbeef): add settlement latency?
     //  * use FPE on the chan id?
     //  * also list failures?

lnrpc/rpc.swagger.json

@@ -2163,6 +2163,16 @@
           "type": "string",
           "format": "uint64",
           "description": "/ The total fee (in milli-satoshis) that this payment circuit carried."
+        },
+        "amt_in_msat": {
+          "type": "string",
+          "format": "uint64",
+          "description": "/ The total amount (in milli-satoshis) of the incoming HTLC that created half the circuit."
+        },
+        "amt_out_msat": {
+          "type": "string",
+          "format": "uint64",
+          "description": "/ The total amount (in milli-satoshis) of the outgoing HTLC that created the second half of the circuit."
         }
       }
     },