refactor: rename Batch to Partition and update related types and channels for consistency

internal/app/etl/loaders/postgres.go

@@ -38,7 +38,7 @@ func (postgresLd *PostgresLoader) ProcessChunk(
 	ctx context.Context,
 	tableInfo config.TargetTableInfo,
 	colNames []string,
-	chunk models.Chunk,
+	chunk models.Batch,
 ) (int, error) {
 	tableId := pgx.Identifier{tableInfo.Schema, tableInfo.Table}
 	_, err := postgresLd.db.CopyFrom(
@@ -60,7 +60,7 @@ func (postgresLd *PostgresLoader) ProcessChunk(
 			}
 		}
 
-		return 0, &custom_errors.LoaderError{Chunk: chunk, Msg: err.Error()}
+		return 0, &custom_errors.LoaderError{Batch: chunk, Msg: err.Error()}
 	}
 
 	return len(chunk.Data), nil
@@ -70,7 +70,7 @@ func (postgresLd *PostgresLoader) Exec(
 	ctx context.Context,
 	tableInfo config.TargetTableInfo,
 	columns []models.ColumnType,
-	chChunksIn <-chan models.Chunk,
+	chChunksIn <-chan models.Batch,
 	chErrorsOut chan<- custom_errors.LoaderError,
 	chJobErrorsOut chan<- custom_errors.JobError,
 	wgActiveChunks *sync.WaitGroup,