Typescript object with key/value pairs that are not known up front

Test.ts

interface ConfigDto extends Record<string, unknown> {}

const myConfigDto: ConfigDto = {
    baseUrl: "http://test.com",
    refershRateInSeconds: 2,
    otherStuff: {a: "a", b: "b"},
    showSpinner: true,
}

console.log(JSON.stringify(myConfigDto, null, 2))
  
//output
<!-- 
{
   "baseUrl":"http://test.com",
   "refershRateInSeconds":2,
   "otherStuff":{
      "a":"a",
      "b":"b"
   },
   "showSpinner":true
} 
-->