Ability to implement an interface into another interface

[berserkore]

Thanks for this great library,
GraphQL spec has now support for implementing an interface into another interface.
Looks like KGraphQL already support this feature, I was able to successfully retrieve the child interface using the spread operator. However, the introspection schema does not show the implementation within the interface and highlight it as an error.

Take the following example:

interface A {
   val prop1: String
 }
 interface B: A {
    override val prop1: String
    val prop2: String
 }

Implements does not show because schema does not explicitly tell it and result to the following introspection:

However it works with a "data class":

interface A {
   val prop1: String
}
data class B (
    override val prop1: String,
    val prop2: String
): A

Here is another reference: graphql/graphql-spec#373