Restrict complex objects in path & query params in Wirespec syntax

[nsmnds]

Currently a user can define complex types in path or query params. This can lead to (unwanted) constructs like:

type Todo {
  name: String,
  isDone: Boolean
}

endpoint CreateTodo POST /todos/{todo: Todo} -> {
  201 -> Unit
}

There are also use cases where it makes more sense, for example for pagination parameters which then be re-used across endpoints. However we see this as an edge-case if we would support this the complexity of the serializers would explode.

Therefore we've decided to restrict this in the syntax.