Quotes should not be implicitly escaped when request body is being stringified

Example:

```
suspend fun putData(): Any {
val response = restClient.put(
"users/bob/name.json",
"""
{ "first": "Jack", "last": "Sparrow" }
""".trimIndent()
)
return response
}
```

Example test:

```
@Test
fun putData() = runBlockingNoJs {
val datastore = DatastoreKorge()

val data = datastore.putData()

println(data)
}
```

This makes it unusable for firebase database:

Start from the Kotlin restClient.put call and trace how its request body is stringified before being sent. Reproduce the example with the JSON body shown; done means quotation marks are not implicitly escaped and the resulting request is usable with Firebase.

Written by the indexing model from the issue text.