refactor: simplify batch processing by removing partition dependency and introducing batch accumulator

internal/app/etl/extractors/main.go

@@ -27,7 +27,6 @@ func sendBatch(ctx context.Context, chBatchesOut chan<- models.Batch, batch mode
 
 func flush(
 	ctx context.Context,
-	partition *models.Partition,
 	batchSize int,
 	batchRows []models.UnknownRowValues,
 	chBatchesOut chan<- models.Batch,
@@ -36,7 +35,7 @@ func flush(
 		return nil
 	}
 
-	batch := models.Batch{Id: uuid.New(), PartitionId: partition.Id, Rows: batchRows}
+	batch := models.Batch{Id: uuid.New(), Rows: batchRows}
 	batchRows = make([]models.UnknownRowValues, 0, batchSize)
 	return sendBatch(ctx, chBatchesOut, batch)
 }