replace async client API / federator msg processing with worker pools (#497)

* replace async client API / federator msg processing with worker pools
* appease our lord-and-saviour, the linter

internal/processing/account/removeblock.go

@@ -54,13 +54,13 @@ func (p *processor) BlockRemove(ctx context.Context, requestingAccount *gtsmodel
 
 	// block status changed so send the UNDO activity to the channel for async processing
 	if blockChanged {
-		p.fromClientAPI <- messages.FromClientAPI{
+		p.clientWorker.Queue(messages.FromClientAPI{
 			APObjectType:   ap.ActivityBlock,
 			APActivityType: ap.ActivityUndo,
 			GTSModel:       block,
 			OriginAccount:  requestingAccount,
 			TargetAccount:  targetAccount,
-		}
+		})
 	}
 
 	// return whatever relationship results from all this