Apply dcat_convert.py to MDTranslator output for ISO records

[SueValente]

What: MDTranslator currently produces DCAT-US v1.1 JSON from ISO 19139 XML. As the pipeline moves to v3.0, ISO-sourced records need to produce v3.0-compatible output. The planned dcat_convert.py migration script (targeted July 2026) converts v1.1 records to v3.0.

This ticket applies dcat_convert.py as a post-MDTranslator step for ISO records, so that pipeline output for ISO sources is v3.0 rather than v1.1.

Likely scope:

• Confirm that dcat_convert.py is implemented as a callable module (not only a CLI tool)
• Add a post-transform step in Record.harvest() that calls dcat_convert.py on the MDTranslator output when schema_type is iso19115_1 or iso19115_2
• Ensure the upgraded output passes v3.0 validation before sync
• Update fill_placeholders and improve_distributions steps if any field names or structures changed in v3.0

Done When:

• ISO WAF records produce v3.0-compatible JSON after the full harvest pipeline
• Records pass v3.0 schema validation
• The Census concity WAF can be harvested end-to-end with v3.0 output
• v1.1 data.json sources are unaffected

Notes:

• Coordinate with whoever is building dcat_convert.py to confirm the module interface
• This ticket assumes Option A from the problem statement (MDTranslator + upgrade) and should not begin until PM confirms that approach
• If Option B (native ISO-to-v3.0 transform) is chosen, this ticket is replaced by a larger implementation effort