raise if a column name has more than 500 characters
fix #2779.

We could do it in datasets, but it's quicker here. I test at the first two points where we handle the columns in the DAG:
- `config-parquet-and-info`
- `first-rows`

raise if a column name has more than 500 characters: fix #2779.

We could do it in datasets, but it's quicker here. I test at the first two points where we handle the columns in the DAG:
- `config-parquet-and-info`
- `first-rows`
