refactor: update column field names in ExtractionQuery struct; enhance logging in consume and process methods

internal/app/db-wrapper/mssql.go

@@ -182,10 +182,10 @@ func (mw *mssqlDbWrapper) QueryFromObject(ctx context.Context, q ExtractionQuery
 
 	sbQuery.WriteString("SELECT ")
 
-	if len(q.columns) == 0 {
+	if len(q.Columns) == 0 {
 		sbQuery.WriteString("*")
 	} else {
-		for i, col := range q.columns {
+		for i, col := range q.Columns {
 			fmt.Fprintf(&sbQuery, "[%s]", col.Name())
 
 			switch col.Type() {
@@ -193,7 +193,7 @@ func (mw *mssqlDbWrapper) QueryFromObject(ctx context.Context, q ExtractionQuery
 				fmt.Fprintf(&sbQuery, ".STAsBinary() AS [%s]", col.Name())
 			}
 
-			if i < len(q.columns)-1 {
+			if i < len(q.Columns)-1 {
 				sbQuery.WriteString(", ")
 			}
 		}