graphql interfaces can extend other interfaces

[hamnis]

This seems like a missing feature in caliban.

caliban/core/src/main/scala/caliban/schema/Types.scala

Lines 120 to 137 in 26fd650

	def makeInterface(
	name: Option[String],
	description: Option[String],
	fields: () => List[__Field],
	subTypes: List[__Type],
	origin: Option[String] = None,
	directives: Option[List[Directive]] = None
	): __Type =
	__Type(
	__TypeKind.INTERFACE,
	name,
	description,
	fields =
	args => if (args.includeDeprecated.getOrElse(false)) Some(fields()) else Some(fields().filter(!_.isDeprecated)),
	possibleTypes = Some(subTypes),
	origin = origin,
	directives = directives
	)

This is supported for types and objects but not interfaces

caliban/core/src/main/scala/caliban/schema/Types.scala

Lines 45 to 62 in 26fd650

	def makeObject(
	name: Option[String],
	description: Option[String],
	fields: List[__Field],
	directives: List[Directive],
	origin: Option[String] = None,
	interfaces: () => Option[List[__Type]] = () => Some(Nil)
	): __Type =
	__Type(
	__TypeKind.OBJECT,
	name,
	description,
	fields =
	args => if (args.includeDeprecated.getOrElse(false)) Some(fields) else Some(fields.filter(!_.isDeprecated)),
	interfaces = interfaces,
	directives = Some(directives),
	origin = origin
	)

The specification allows this: https://spec.graphql.org/draft/#sec-Interfaces