chore: Warn on generated columns

[caike]

Fixes #71

What kind of change does this PR introduce?

Prints a warning upon detecting generated columns.

What is the current behavior?

No warnings and user might not be aware that generated columns are being ignored from publication.

What is the new behavior?

Warns users about generated columns being excluded from the publication. For each table with a detected generated column, a warn message like so will be displayed:

2025-11-20T16:35:20.050149Z WARN apply_worker{pipeline_id=1 publication_name="full_pub"}:table_sync_worker{pipeline_id=1 publication_name="full_pub" table_id=16393}: etl::replication::client: Table 16393 contains generated columns that will NOT be replicated. Generated columns are not supported in PostgreSQL logical replication and will be excluded from the ETL schema. These columns will NOT appear in the destination.

Additional context

Tested with PostgreSQL 17.6

[iambriccardo]

@codex review

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[iambriccardo]

Thanks for the contribution, however adding this check within the CTE seems to add unnecessary complexity.

I would rather just add a separate query that emits the warning before querying the actual column schemas. This way it's separate and clearer.

[caike]

Figured that keeping at least the table_id in the warn message would be helpful and at no performance cost