Nucivic open data schema map dkan issue 37 group list endpoint

NuCivic/nucivic-internal#37
This PR depends on f64338a69a8e1542a3d1a2c5e5bb8caab7bd0770 NuCivic/nucivic-internal#36

### Accepting test 
Running:
```bash
drush fr open_data_schema_map_dkan
```
When I go to /admin/config/services/odsm then I should see "CKAN Group List" listed.