Support for schema enum extensions?

[levibuzolic]

relay/compiler/crates/schema/src/in_memory/mod.rs

Lines 732 to 734 in 14550c8

	TypeSystemDefinition::SchemaExtension { .. } => todo!("SchemaExtension"),
	TypeSystemDefinition::EnumTypeExtension { .. } => todo!("EnumTypeExtension"),
	TypeSystemDefinition::UnionTypeExtension { .. } => todo!("UnionTypeExtension"),

Is there already work in progress for the new Rust compiler to support EnumTypeExtension and some of the other features here marked as todo? We're looking to upgrade to Relay 13, but trying to work out if we'll need to work around the missing extension support here.

[alunyov]

Yeah, I think we should to add this. We don't use this internally, but we need this to complete the schema API.