Backend: BTC certificiranje detail

GitHub Issue: #250

Backend task for the BTC certificiranje detail page (GET /btc-certifications/{certificationId}) – check the header, komisija, candidates and the caller's Usmeni ispit status against the API spec and DB structure, permissions, implement, and verify against the spec.

Docs: BTC certificiranje detail Spec: GET /btc-certifications/{certificationId} (getBtcCertificationDetail), BtcCertificationDetail in api-docs/openapi.yaml DB: BtcCertifications, BtcCertificationCandidates, BtcCertificationBoardMembers, BtcCertificationGrades in api/database/create_schema.sql

The detail endpoint is also used by the edit form and for the header / candidate name on the Usmeni ispit form.

1. Double check API spec and DB structure

• Header: name, status, brand, date, “Komisija:” list → name, status, brandCode, startDate / endDate, boardMembers (active only). The docs recommend showing the date range; the response has both dates.
• Candidates: name, e-mail, partner → fullName, email, partnerId. The partner name comes from the partner lookup. Check the frontend can resolve it (or add partnerName).
• Usmeni ispit row: the caller’s status → myOralExamCompleted; “Otvori” only for komisija members → isBoardMember. Both use active membership: a removed member sees no “Otvori”. Confirm.
• “UREDI CERTIFICIRANJE” is shown for Aktivni / Nadolazeći and only to users with btc-certifications.edit (Trainer; hidden from BTC evaluators, per the docs). The frontend decides this from status and GET /me/permissions.
• hasGrades per candidate (any member’s grade, removed members included, or a written exam score) is used by the edit form to hide “–”.
• Komisija members can keep editing after Zaključeno and in any certificiranje status. Nothing here blocks that.
• Roles and permissions: btc-certifications.access (Trainer, BTC evaluator), all certificiranja.
• DB: removed members (DeletedAt not null) are left out of boardMembers.

2. Implementation

• Roles and permissions: require btc-certifications.access → 403.
• DB: load the certificiranje (not deleted, else 404), active members, candidates, and the caller’s grades for all candidates (one query), plus a “has grades” flag per candidate (one query with EXISTS).
• isBoardMember: the caller’s user id matches an active BtcCertificationBoardMembers row.
• myOralExamCompleted: use the shared Zaključeno helper from Backend: Form – Modul 5 – Usmeni ispit (grade a + all 7 categories). null when isBoardMember is false.

3. Verify implementation against spec

• Shape and status codes match getBtcCertificationDetail.
• Komisija member: isBoardMember true, status per candidate correct after saving a full and a partial form.
• Trainer not in komisija: isBoardMember false, myOralExamCompleted null.
• Removed member: not in boardMembers, isBoardMember false, their grades still make hasGrades true.
• Unknown / deleted id → 404. User without access → 403.

Done when

The detail page shows the header, komisija and candidates, with the caller’s own Usmeni ispit status and “Otvori” for komisija members only.