Should `UUID` be a valid RefType?

[hasezoey]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the issue has not already been raised

Issue

I have noticed that UUID is not part of RefType and have wondered if it should be valid (as Buffer is).

mongoose/types/index.d.ts

Lines 565 to 575 in b7b257e

	export type RefType =
	| number
	| string
	| Buffer
	| undefined
	| Types.ObjectId
	| Types.Buffer
	| typeof Schema.Types.Number
	| typeof Schema.Types.String
	| typeof Schema.Types.Buffer
	| typeof Schema.Types.ObjectId;

[vkarpov15]

It should be, I'll test this out.