## GET /api/v2/placement-groups/candidates

**List VPS placement group candidates**

Return VPS candidates owned by the caller. `compatibilityKey` is opaque; consumers only compare keys for equality and must not interpret it.

### Related Endpoints

- `GET /api/v2/placement-groups`: List VPS placement groups
- `POST /api/v2/placement-groups`: Create a VPS placement group
- `GET /api/v2/placement-groups/{id}`: Get VPS placement group detail

### Headers

- `Accept`: application/json
- `Authorization`: Bearer YOUR_API_KEY
- Required API scope: `read:vm`

### Request Example

```bash
curl -X GET "https://cloud.hostup.se/api/v2/placement-groups/candidates" \
  -H "Authorization: Bearer YOUR_API_KEY" \
  -H "Accept: application/json"
```

### Response Schema

- `candidates` (array<object>, required)
- `candidates[].id` (string, required) Example: `vps_01hxa3b4c5d6e7f8g9h0j1k2m3`
- `candidates[].name` (string, required) Example: `db-primary`
- `candidates[].instanceUrl` (string, required) Example: `/instance/vps_01hxa3b4c5d6e7f8g9h0j1k2m3`
- `candidates[].compatibilityKey` (string, required, nullable): Nullable (may be null when not applicable). Example: `pgcmp_9f6a3b2c1d0e8a7b`
- `candidates[].placementGroupId` (string, required, nullable): Nullable (may be null when not applicable). Example: `null`
- `candidates[].available` (boolean, required) Example: `true`
- `candidates[].reason` (string, required, nullable): Nullable (may be null when not applicable). Example: `null`

### Responses

#### 200 - Candidate VPS snapshot.
```json
{
  "candidates": [
    {
      "id": "vps_01hxa3b4c5d6e7f8g9h0j1k2m3",
      "name": "db-primary",
      "instanceUrl": "/instance/vps_01hxa3b4c5d6e7f8g9h0j1k2m3",
      "compatibilityKey": "pgcmp_9f6a3b2c1d0e8a7b",
      "placementGroupId": null,
      "available": true,
      "reason": null
    }
  ]
}
```

#### 400 - Invalid request. The response body is an RFC 7807 Problem Details document.
```json
{
  "type": "https://developer.hostup.se/errors/invalid_request",
  "title": "Invalid request",
  "status": 400,
  "detail": "The request body failed validation.",
  "code": "invalid_request",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z",
  "errors": [
    {
      "pointer": "/items/0/domainName",
      "detail": "`domainName` is required.",
      "code": "invalid_request"
    }
  ]
}
```

#### 401 - Unauthorized. Authentication is required.
```json
{
  "type": "https://developer.hostup.se/errors/unauthorized",
  "title": "Unauthorized",
  "status": 401,
  "detail": "Authentication is required.",
  "code": "unauthorized",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```

#### 403 - Forbidden. The caller lacks a required scope or does not own the resource.
```json
{
  "type": "https://developer.hostup.se/errors/forbidden",
  "title": "Forbidden",
  "status": 403,
  "detail": "The caller lacks a required scope or does not own the resource.",
  "code": "forbidden",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```

#### 404 - Not found. The resource does not exist or is not owned by the caller.
```json
{
  "type": "https://developer.hostup.se/errors/not_found",
  "title": "Not found",
  "status": 404,
  "detail": "The requested resource could not be found.",
  "code": "not_found",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```

#### 429 - Rate limited. Retry after the limit resets. 429 responses include `Retry-After` seconds plus `X-RateLimit-*` headers.
```json
{
  "type": "https://developer.hostup.se/errors/rate_limit_exceeded",
  "title": "Too many requests",
  "status": 429,
  "detail": "Too many requests. Retry after the limit resets.",
  "code": "rate_limit_exceeded",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```

#### 500 - Internal error. Retry later or contact support if the issue persists.
```json
{
  "type": "https://developer.hostup.se/errors/internal_error",
  "title": "Internal server error",
  "status": 500,
  "detail": "An unexpected error occurred. Retry later or contact support if the issue persists.",
  "code": "internal_error",
  "instance": "/api/v2/resource",
  "requestId": "req_01hxa3b4c5d6e7f8g9h0j1k2m3",
  "timestamp": "2026-04-27T12:34:56.000Z"
}
```