CORE-5832 Updated /apps endpoint responses.

Added swagger docs for responses from the /apps, /apps/categories, and /apps/categories/:id endpoints.
Fixed response for /apps/categories?public=false endpoint.
Refactored /apps/{app-id}/ui response.
CORE-5386 Refactor data_source id_v187 column.

Renamed to display_order, since that is how it's being used by the element listing endpoint.
CORE-5832 Initial refactor of get-workflow-elements endpoint.

Renamed endpoint to /apps/elements/:type and refactored for new db schema.