UTXO spent tracking refactor

refs #1301

frontend/src/app/interfaces/websocket.interface.ts

@@ -16,7 +16,7 @@ export interface WebsocketResponse {
   data?: string[];
   tx?: Transaction;
   rbfTransaction?: Transaction;
-  utxoSpent?: boolean;
+  utxoSpent?: object;
   transactions?: TransactionStripped[];
   loadingIndicators?: ILoadingIndicators;
   backendInfo?: IBackendInfo;