lnrpc/invoicesrpc: add new invoice ref LookupInvoiceV2 method

In this commit, we add a new `LookupInvoiceV2` method attached to the
invoice RPC sub-server. Compared to the existing version, this version
allows an invoice to be looked up by an invoice ref. This enables users
to query an AMP invoice based on a specific _set ID_, so they can get
the information related to the set of cumulative settles to that
invoices.

lnrpc/invoicesrpc/invoices.pb.json.go

@@ -139,4 +139,29 @@ func RegisterInvoicesJSONCallbacks(registry map[string]func(ctx context.Context,
 		}
 		callback(string(respBytes), nil)
 	}
+
+	registry["invoicesrpc.Invoices.LookupInvoiceV2"] = func(ctx context.Context,
+		conn *grpc.ClientConn, reqJSON string, callback func(string, error)) {
+
+		req := &LookupInvoiceMsg{}
+		err := marshaler.Unmarshal([]byte(reqJSON), req)
+		if err != nil {
+			callback("", err)
+			return
+		}
+
+		client := NewInvoicesClient(conn)
+		resp, err := client.LookupInvoiceV2(ctx, req)
+		if err != nil {
+			callback("", err)
+			return
+		}
+
+		respBytes, err := marshaler.Marshal(resp)
+		if err != nil {
+			callback("", err)
+			return
+		}
+		callback(string(respBytes), nil)
+	}
 }