curl -X POST "https://app.talkover.ai/api/v1/calendars/calendar-uuid-1/providers" \
  -H "Authorization: Bearer talq_your_environment_token_here" \
  -H "Content-Type: application/json" \
  -d '{
    "provider": "calendar_provider_a",
    "redirect_uri": "https://example.com/oauth/calendar/callback"
  }'

{
  "success": true,
  "data": {
    "id": "conn-uuid-1",
    "provider": "calendar_provider_a",
    "authorization_url": "https://provider.example.com/oauth/authorize?.",
    "is_active": false
  }
}