feat: add database wrapper interfaces for mssql and postgres

Introduce a DB dialect interface and per-dialect wrappers that expose connection, query and column type operations with pre/post SQL hooks.

internal/app/custom_errors/loader.error.go

@@ -21,11 +21,14 @@ func (e *LoaderError) Error() string {
 func LoaderErrorHandler(
 	ctx context.Context,
 	retryConfig config.RetryConfig,
+	maxChunkErrors int,
 	chErrorsIn <-chan LoaderError,
 	chBatchesOut chan<- models.Batch,
 	chJobErrorsOut chan<- JobError,
 	wgActiveBatches *sync.WaitGroup,
 ) {
+	definitiveErrors := 0
+
 	for {
 		if ctx.Err() != nil {
 			return
@@ -42,6 +45,7 @@ func LoaderErrorHandler(
 
 			if err.Batch.RetryCounter >= retryConfig.Attempts {
 				wgActiveBatches.Done()
+				definitiveErrors++
 				jobError := JobError{
 					ShouldCancelJob: false,
 					Msg:             fmt.Sprintf("Batch %v reached max retries (%d)", err.Batch.Id, retryConfig.Attempts),
@@ -54,6 +58,20 @@ func LoaderErrorHandler(
 					return
 				}
 
+				if maxChunkErrors > 0 && definitiveErrors >= maxChunkErrors {
+					fatalError := JobError{
+						ShouldCancelJob: true,
+						Msg:             fmt.Sprintf("Chunk error limit reached (%d)", maxChunkErrors),
+						Prev:            &err,
+					}
+
+					select {
+					case chJobErrorsOut <- fatalError:
+					case <-ctx.Done():
+						return
+					}
+				}
+
 				continue
 			} else {
 				jobError := JobError{