Federation search endpoint

[Imene-Amirat]

New endpoint: /api/federation/search

• Add a new /api/federation/search endpoint that queries the external base4nfdi API Gateway

• Maps the external API response fields to EarthPortal's format :
  - label → prefLabel
  - synonyms → synonym
  - descriptions → definition

• Reuses the existing Class.read_only + submission + page_object mechanism so the serializer generates the same JSON structure (@links, @context, pagination) the frontend expects

Limitations :

• totalCount: Always returns 100 because the API Gateway returns a maximum of 100
• matchType: API Gateway doesn't tell us which field matched the query
• links.ui: The serializer generates this URL
  http://#{LinkedData.settings.ui_host}/ontologies/#{acronym}?p=classes&conceptid=#{id}
  using a global config ui_host (default: bioportal.bioontology.org, in prod it will be earthportal.eu )
  but for federation all results will point to earthportal.eu even if they come from AgroPortal or EcoPortal, because ui_host is the same for every result
  instead :
  the API Gateway provides source_url field
• ontologyType: Not returned by the API Gateway

[Copilot]

Pull request overview

Adds a new federation search API endpoint that proxies queries to the base4nfdi API Gateway and adapts results into EarthPortal’s existing class search/page serialization format.

Changes:

• Introduces GET /api/federation/search querying the external base4nfdi API Gateway.
• Maps gateway fields into EarthPortal’s expected class fields (label→prefLabel, synonyms→synonym, descriptions→definition).
• Wraps results using Class.read_only + submission + page_object to reuse existing JSON structure (links/context/pagination).

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.

[Copilot]

Avoid returning the raw upstream response body to clients on gateway errors; it can be large and may leak upstream details. Prefer a generic client-facing message and log the gateway body/status for debugging.

Suggested change

	error response.status, "API Gateway error: #{response.body}"
	Rails.logger.error("API Gateway error: status=#{response.status}, body=#{response.body}") if defined?(Rails) && Rails.respond_to?(:logger) && Rails.logger
	error response.status, "API Gateway error: upstream service returned an error"

[Copilot]

This endpoint ignores page/pagesize request params and always returns all gateway results. Because page_object assumes the collection is already paginated, this can produce responses where itemsPerPage doesn’t match the number of returned members and pagination links become misleading. Please apply local slicing (using page_params + offset_and_limit) before building the page object.

Suggested change

	reply 200, page_object(docs, total_found)
	page, page_size = page_params
	offset, limit = offset_and_limit(total_found, page, page_size)
	paginated_docs = docs.slice(offset, limit) || []
	reply 200, page_object(paginated_docs, total_found)