RPC codegen support inherit methods

[martin-ncs]

The current codegen only supports methods defined inline, so we can't extend the RPC definition interface, which is useful for re-using method definitions.

Here's a quick example:

interface SharedCalls {
    suspend fun inherit()
}

interface DefinitionRpc : RPC, SharedCalls {
    suspend fun inline()
}

suspend fun executeRpc() {
    val http = HttpClient {
        installRPC()
    }
    val rpc = http.rpc().withService<DefinitionRpc>()

    // client code expects these to work
    rpc.inline()
    rpc.inherit()
}

As the codegen wont generate the inheritmethod so the class DefinitionRpcClient wont compile, leading into this error:

Class 'DefinitionRpcClient' is not abstract and does not implement abstract member public abstract suspend fun inherit()

[Mr3zee]

Hi! Thank you for the ticket! We will consider implementing it after K2 support