Support watching custom scripts (#71)

* Add external script repo

* Add external script repo impls

* Remove leftover

* Support (un)watching external scripts

* Prevent send notifications for unsubscribed scripts/acounts

* Fixes

api-spec/protobuf/ocean/v1/account.proto

@@ -156,4 +156,4 @@ message DeleteAccountRequest{
   // Account namespace or label.
   string account_name = 1;
 }
-message DeleteAccountResponse{}
+message DeleteAccountResponse{}

api-spec/protobuf/ocean/v1/notification.proto

@@ -10,6 +10,15 @@ import "ocean/v1/types.proto";
 // server-side stream or by subscribing webhooks invoked whenever an event 
 // occurs.
 service NotificationService {
+  // WatchExternalScript allows to get notified about utxos/txs related to the given
+  // external script, ie. not derived from a wallet account.
+  // The service answers with the label assigned to the given script.
+  // The label is used as identifier of the utxos/txs received from the streams.
+  rpc WatchExternalScript(WatchExternalScriptRequest) returns(WatchExternalScriptResponse);
+  // UnwatchExternalScript allows to stop watching for the script identified with
+  // the given label.
+  rpc UnwatchExternalScript(UnwatchExternalScriptRequest) returns(UnwatchExternalScriptResponse);
+
   //**************//
   //   STREAMS    //
   //**************//
@@ -24,14 +33,29 @@ service NotificationService {
   //***************//
 
   // Adds a webhook registered for some kind of event.
-  rpc AddWebhook(AddWebhookRequest) returns(AddWebhookResponse){}
+  rpc AddWebhook(AddWebhookRequest) returns(AddWebhookResponse);
 
   // Removes some previously added webhook.
-  rpc RemoveWebhook(RemoveWebhookRequest) returns(RemoveWebhookResponse){}
+  rpc RemoveWebhook(RemoveWebhookRequest) returns(RemoveWebhookResponse);
 
   // Returns registered webhooks.
-  rpc ListWebhooks(ListWebhooksRequest) returns(ListWebhooksResponse){}
+  rpc ListWebhooks(ListWebhooksRequest) returns(ListWebhooksResponse);
+}
+
+message WatchExternalScriptRequest {
+  // The script to watch.
+  string script = 1;
+  // Optional: the private blinding key in case the script locks confidential utxos to unblind.
+  string blinding_key = 2;
+}
+message WatchExternalScriptResponse {
+  string label = 1;
+}
+
+message UnwatchExternalScriptRequest {
+  string label = 1;
 }
+message UnwatchExternalScriptResponse {}
 
 message TransactionNotificationsRequest{}
 message TransactionNotificationsResponse{

internal/app-config/config.go

@@ -267,7 +267,8 @@ func (c *AppConfig) notificationService() *application.NotificationService {
 	}
 
 	rm, _ := c.repoManager()
-	c.notifySvc = application.NewNotificationService(rm)
+	bcs, _ := c.bcScanner()
+	c.notifySvc = application.NewNotificationService(rm, bcs)
 	return c.notifySvc
 }
 

internal/core/application/account_service.go

@@ -269,29 +269,6 @@ func (as *AccountService) registerHandlerForWalletEvents() {
 			as.bcScanner.StopWatchForAccount(event.AccountName)
 		},
 	)
-	// Start watching for when utxos are spent as soon as they are added to the storage.
-	as.repoManager.RegisterHandlerForUtxoEvent(
-		domain.UtxoAdded, func(event domain.UtxoEvent) {
-			accountName := event.Utxos[0].AccountName
-			as.bcScanner.WatchForUtxos(accountName, event.Utxos)
-		},
-	)
-
-	// In background, make sure to watch for all utxos to get notified when they are spent.
-	go func() {
-		utxos, err := as.repoManager.UtxoRepository().GetAllUtxos(
-			context.Background(),
-		)
-		if err != nil {
-			as.warn(err, "account service: error while getting all utxos")
-			return
-		}
-		for _, u := range utxos {
-			if !u.IsSpent() {
-				as.bcScanner.WatchForUtxos(u.AccountName, []domain.UtxoInfo{u.Info()})
-			}
-		}
-	}()
 }
 
 func (as *AccountService) listenToUtxoChannel(