Adding POST /tx API to bitcoind mode

fixes #777

backend/src/api/bitcoin/bitcoin-api-abstract-factory.ts

@@ -11,6 +11,7 @@ export interface AbstractBitcoinApi {
   $getAddress(address: string): Promise<IEsploraApi.Address>;
   $getAddressTransactions(address: string, lastSeenTxId: string): Promise<IEsploraApi.Transaction[]>;
   $getAddressPrefix(prefix: string): string[];
+  $sendRawTransaction(rawTransaction: string): Promise<string>;
 }
 export interface BitcoinRpcCredentials {
   host: string;