Ability to retrieve participant data through API

[aliflaming]

On interviews, a key part of our session analysis is using the session metadata on session completion status and merging with participant data in order to calculate metrics on session completion per interview type.

Right now, getting the participant data is a manual export process that we unable to build into labs. If we could also access the participant data via the API, we can fully automate our analysis in Labs.

We are doing this analysis manually this week, but ideally want to get it up and running on labs next week. What is the LOE of adding this, and how long do you estimate it would take?

(let's discuss in our strategy call, against the other current priorities)

[ocs-percy]

Design: Participant Data Read API

Approach

Extend /api/participants into a proper ViewSet with list + retrieve support, keeping the existing POST endpoint untouched for backwards compatibility. Use public_id (UUID) as the URL lookup key — stable, and avoids putting phone numbers/emails in URLs.

New API scope: participants:read (parallel to existing participants:write)

---

Endpoints

GET /api/participants/

Returns a paginated list of participants for the team, with their per-experiment data.

Query params:

• ?experiment=<public_id> — filter to participants who have data for a specific experiment (recommended for the analysis use case)
• ?platform=whatsapp — filter by platform
• ?identifier=... — filter by identifier

Response:

{
  "results": [
    {
      "id": "<public_uuid>",
      "identifier": "+27456789",
      "name": "John Smith",
      "platform": "whatsapp",
      "remote_id": "",
      "data": [
        {
          "experiment": "<experiment_public_id>",
          "data": { "interview_type": "baseline", "..." : "..." }
        }
      ]
    }
  ]
}

GET /api/participants/{public_id}/

Same shape, single record.

---

Notes

• data is always included but scoped to experiments matching the ?experiment filter if provided. Without the filter, all ParticipantData records for each participant are returned. The query will use prefetch_related to keep this efficient.
• The existing POST /api/participants write endpoint and its scope (participants:write) are unchanged.
• ParticipantData.data is encrypted at rest but transparent to DRF — no special serializer handling needed.
• The /api/sessions/ endpoint already exposes participant identifier and remote_id, so consumers can join on those fields for the session-completion analysis use case.