code generation for deserialisation does not work with Classes, only Structs

[theffc]

Description

As a user I want to create my Custom Components using Classes instead of Structs, and still would not need to manually create code for Decodable conformance.

Problem

We provide a tool to our users to automatically generate Decodable conformance for custom components. But that tool does not work with Classes, only Structs.

Expected behaviour

• solution won't change how it works with Structs, only extend to also work with Classes
• the API (AutoDecodable) should be the same

[theffc]

we will depreciate this due to a feeling that our users would probably not use Sourcery. If that changes, we can do that again.