feat: implement loader error handling and refactor chunk processing in migration job

cmd/go_migrate/extractor-error-handler.go

@@ -81,20 +81,18 @@ func ExtractorErrorFromLastRowMssql(lastRow UnknownRowValues, indexPrimaryKey in
 	if !ok {
 		currentBatch := *batch
 		currentBatch.RetryCounter = maxRetryAttempts
-		exError := ExtractorError{
+		return ExtractorError{
 			Batch:     currentBatch,
 			HasLastId: true,
 			Msg:       fmt.Sprintf("Couldn't cast last id value as int: %s", previousError.Error()),
 		}
-		return exError
 
 	}
 
-	exError := ExtractorError{
+	return ExtractorError{
 		Batch:     *batch,
 		HasLastId: true,
 		LastId:    lastId,
 		Msg:       previousError.Error(),
 	}
-	return exError
 }