JSON to Kotlin Data Class Converter

From a JSON sample to a Kotlin data class

A data class is the right container for a decoded payload. The compiler writes equals, hashCode, copy and toString from the constructor properties, which is exactly what a transfer object needs and nothing beyond it. Properties are emitted as val, so the model is immutable once built.

What the serialiser still needs from you

• An annotation. The class is library-neutral as generated. kotlinx.serialization needs @Serializable on the class; Moshi and Jackson need their own adapters or module registration.
• Key mapping. Names are camelCased, so a created_at key becomes createdAt. Add @SerialName("created_at") or the equivalent for your library.
• Nullability. Kotlin types are non-null unless marked, and every property here arrives non-null. Add ? to anything the server may send as null.
• Absent against null. In kotlinx.serialization, giving a property a default value makes its key optional in the input, while marking it nullable only permits an explicit null. Those are different guarantees, and no single sample can tell them apart.
• Collections are typed from the first element, and Long against Double is decided by whether the sample value had a decimal point.

For the same API on iOS, JSON to Swift emits the Codable equivalent, and JSON to Dart covers a Flutter client.