curl --request PUT \
  --url http://localhost:3000/api/user/institutionJoin \
  --header 'Content-Type: application/json' \
  --header 'x-access-token: <api-key>' \
  --data '
{
  "joinId": "abc123xyz"
}
'

{
  "success": true,
  "message": "Successfully joined institution",
  "userInstitution": {
    "_id": "<string>",
    "institution": "<string>",
    "status": "active"
  }
}