Support `@JsonDiscriminator`

[aSemy]

kxs-ts-gen should detect @JsonDiscriminator, and use the @SerialName as a hardcoded value

@Serializable
@JsonDiscriminator("type")
sealed class SomeClass {
  val id: String
}

@SerialName("named")
@Serializable
data class NamedSomeClass(
  override val id: String,
  val name: String,
) : SomeClass()

Should convert to something like...

interface SomeClass<T extends "named"> {
  id: string;
  type: T
}

interface NamedSomeClass extends SomeClass {
  id: string;
  type: "named"
}