Test integration credentials

Validate credentials against the provider's authentication endpoint without activating the integration. Used by the activation wizard to surface credential errors before the merchant commits to a sync schedule. Returns `{ valid: true }` on success or `{ valid: false, reason }` with the provider's error message on failure. No state is persisted. --- **Related endpoints** - `POST /integrations/{provider}/activate` — Activate integration - `POST /integrations/{provider}/deactivate` — Deactivate integration - `GET /integrations/{provider}` — Get integration status - `POST /integrations/{provider}/rotate` — Rotate integration credentials - `POST /integrations/{provider}/sync` — Trigger manual sync - `POST /integrations/{provider}/invoices/{externalInvoiceId}/refresh` — Refresh a single PracticeHub invoice - `GET /integrations/{provider}/invoices/{externalInvoiceId}/refresh-status` — Get demand invoice refresh status - `GET /integrations` — List all integrations **Common errors** - `401 authentication_error` — missing, invalid, expired, or revoked credential. Codes: `authentication_failed`, `invalid_api_key`, `expired_api_key`, `api_key_revoked`, `session_invalid`, `merchant_required`. Carries a `WWW-Authenticate: Bearer` challenge. **Idempotency** Pass an `Idempotency-Key` header (UUID v4 recommended) to make retries safe. Keys are valid for 24 hours; see [the idempotency guide](/docs/fundamentals/idempotency).

curl -X POST "https://api.revkeen.com/v2/integrations/practicehub/test" \
  -H "x-api-key: $REVKEEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "credentials": {
      "apiKey": "string",
      "baseUrl": "https://example.com",
      "appName": "RevKeen",
      "appEmail": "info@revkeen.com"
    }
  }'

{  "valid": true,  "error": "string"}