Schema - Fix theme/theme_es/theme_eu fields

[mjanez]

Maintain consistency in the naming of field_names, utilizing EU INSPIRE themes as a default, and adding suffixes to any national values.

• theme: INSPIRE Themes in all schemas. Spatial data themes, as defined in the Annexes of the INSPIRE Directive, compatibles with DCAT and also DCAT-AP/GeoDCAT-AP. (E.g: https://www.w3.org/TR/vocab-dcat-3/#ex-spatial-coverage-bbox)
• theme_{code}: For instance, theme_eu for MDR Themes or theme_es for spanish NTI-RISP vocabulary themes.

Adaptation is also required:

• [x] ckan-docker (Solr fields, .env, etc.)
• [x] ckan-ogc theme/theme_inspire (Harvester/Ingester fields)
• [ ] ckan-pycsw (theme == <gmd:keyword> from Thesaurus.)

[mjanez]

• [ ] Add auto theme_eu to theme_es in GeoDCA-AP ES Schema using the dcat_ap prop in the Schema. https://github.com/mjanez/ckanext-scheming_dcat#geodcat-ap-es

[mjanez]

It is better to keep theme, like INSPIRE themes, and theme_{isocode}, like DCAT's.