Topics dropdown should be included

Since the datasets are classified by Topics, CKAN should include required fields for one (or multiple) Topic areas. Users could select from a picklist. For example, Climate Change, Agriculture. As new Topics are added, the picklist could be updated. Data Stewards could edit the existing datasets by tagging them with the new Topics. This is different from relying on the uncontrolled vocabulary of the Keywords - this is less accurate for search purposes.

The issue names CKAN but no repository file, entry point, or test. Start by locating the dataset metadata configuration and existing Keywords field, then determine how a controlled Topic picklist and edits to existing datasets would be represented; done means Topics can be selected consistently and used for accurate search.

Written by the indexing model from the issue text.