curl -X PUT "https://app.talkover.ai/api/v1/calendars/calendar-uuid-1/members/member-uuid-2" \
  -H "Authorization: Bearer talq_your_environment_token_here" \
  -H "Content-Type: application/json" \
  -d '{ "role": "viewer" }'

{
  "success": true,
  "data": {
    "id": "member-uuid-2",
    "role": "viewer"
  }
}