curl --request PUT \
  --url https://rest.hotfix.jobs/v1/employer/applications/{application_id}/fields/{key} \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "value": "175000"
}
'

const options = {
  method: 'PUT',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({value: '175000'})
};

fetch('https://rest.hotfix.jobs/v1/employer/applications/{application_id}/fields/{key}', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

import requests

url = "https://rest.hotfix.jobs/v1/employer/applications/{application_id}/fields/{key}"

payload = { "value": "175000" }
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

response = requests.put(url, json=payload, headers=headers)

print(response.text)

{
  "custom_fields": [
    {
      "id": "8b0f6f7e-1c2d-4e3f-9a8b-7c6d5e4f3a21",
      "key": "salary_expectation",
      "name": "Salary expectation",
      "type": "currency",
      "value": "175000",
      "display": "$175,000"
    }
  ]
}