⚙️ Backend Issue — Public Sample Landing Page Endpoint (by IGSN)

🎯 Goal

Provide a public, read-only endpoint that serves all relevant metadata for a sample identified by its IGSN (pid), without requiring authentication (session_id). This endpoint will power the Sample Landing Page in SEPIA and serve as the target URL for IGSN registrations (e.g., linked from DataCite records).

🧩 Implementation Details

1. New Endpoint

Endpoint:
```
GET /sample/{igsn}/public
```
Purpose: Retrieve a full metadata representation of a sample using its IGSN (PID). Accessible without authentication to allow public visibility for registered samples.
Access Control:
- No session_id required.
- Only samples with a valid, registered IGSN should be resolvable.
- Return 404 if no sample matches the given IGSN.

Example Request:

GET /sample/IGSN:HZB000123/public

Example Response:

{
  "igsn": "IGSN:HZB000123",
  "name": "Catalyst Sample X",
  "description": "High-surface catalyst tested under beamline A.",
  "sample_type": {
    "name": "Catalyst",
    "description": "Solid catalyst type"
  },
  "creator": {
    "full_name": "Dr. Alice Example",
    "affiliation": "HZB"
  },
  "keywords": ["Catalyst", "Surface Analysis"],
  "dates": [
    {"type": "Created", "value": "2024-05-03"},
    {"type": "Analyzed", "value": "2024-06-15"}
  ],
  "related_items": [
    {"type": "Publication", "title": "Surface Chemistry Study", "url": "https://doi.org/..."}
  ],
  "created_at": "2024-05-03T10:30:00Z",
  "updated_at": "2024-09-14T12:40:00Z"
}

2. Implementation Notes

Extend OpenAPI spec to define this new public route.
Implement using connexion with operationId: "sample.read_public_by_igsn".
Query Sample by pid (IGSN) instead of id.
Include related objects:
- sample_type
- sample_users (with limited info: full_name, affiliation)
- keywords, dates, and related_items
Use a dedicated serializer schema (e.g. SamplePublicSchema) that omits internal or sensitive fields.
Optionally apply response caching (e.g., TTLCache from cachetools with 10 min live) to reduce database load for public views.
Return minimal error payloads (404, 500) to avoid leaking backend details.

3. Integration with IGSN Minting

When an IGSN is minted (via /sample/{id}/mint_igsn), SEPIA should store the landing page URL:
```
https://sepia.helmholtz-berlin.de/sample/{igsn}/public
```
This URL will be sent to DataCite as the landing page in the registration metadata.

🧪 Testing

Works with valid IGSN, returns full metadata.
Returns 404 for unknown or unregistered IGSN.
No session_id required.
Includes correct related data (sample type, users, keywords, dates).
Data structure matches frontend requirements.
Performance acceptable for public queries.

🏷️ Labels

backend feature igsn sample landing-page public-endpoint priority::high