Expose holder_name counts for Italy (dati.gov.it)

[aborruso]

Problem

For Italian datasets, the real PA owner is captured in holder_name, while organization often reflects the technical publisher (e.g., Agenzia delle Entrate datasets appear under GeoDati - RNDT). Today the tools surface only organization counts, which is misleading for Italian portals.

Proposal

Add a tool or specialize existing outputs to include holder_name counts for Italy (dati.gov.it):

• When server_url is https://www.dati.gov.it/opendata (or aliases), include holder-name facets/counts alongside organization counts.
• Prefer holder_name in summaries for Italy, and treat organization as a technical publisher.
• Provide a clear note in output for Italy: “PA titolare = holder_name”.

Example

User asks “top organizations”: return holder_name ranking for Italy, optionally with organization as a secondary field.

Rationale

holder_name is present for all datasets on dati.gov.it and maps to the real PA. This better matches user expectations and avoids confusion.

Acceptance Criteria

• Tool output for Italian portal includes holder_name counts.
• Documentation clarifies holder_name usage for Italy.
• Behavior is portal-specific (do not change other CKAN portals).