[REQ] [kotlin-server] Add kotlinx serialization support

Is your feature request related to a problem? Please describe.

We do use Ktor with kotlinx as our serialization library which is currently not supported by the kotlin-server generator. But we really like to use the kotlin-server generator for our project. Currently, we do adopt the existing mustache files manually in our project to add the @Serializable annotation ourselves. But of course we would prefer to have it directly supported by the generator itself.

Describe the solution you'd like

Add kotlinx as additional option to serializationLibrary.

Describe alternatives you've considered

We thought about using the kotlin generator as it supports kotlinx via multiplatform. But having even the paths/routes generated by the generator is sth. we really want to keep and therefore we do prefer the kotlin-server generator.

Additional context

Start at the kotlin-server generator's serializationLibrary option and compare it with the kotlin generator's kotlinx support via multiplatform. Trace the existing mustache files used for Kotlin server generation; done means kotlinx is selectable and generated output supports @Serializable while retaining generated paths and routes.