types: improve typing for transform option to toJSON and toObject

[vkarpov15]

Fix #15479

Summary

Better typing for the transform() function, 2nd arg should be a raw doc type by default not Record<string, any>.

Maybe worthwhile to postpone this for a minor release, WDYT @hasezoey ?

Examples

[Copilot]

Pull Request Overview

Adds a type-level test to verify that the transform callback on toJSON receives the correct raw document type and enforces proper return typing.

• Introduces a new test function gh15479 to cover transform option typing
• Defines a transform callback with doc and ret parameters and uses toJSON generics
• Verifies that the returned object omits testField when using the transformed return type

Comments suppressed due to low confidence (1)

test/types/schema.test.ts:1816

• [nitpick] The test function name gh15479 is not descriptive. Consider renaming it to something like testTransformOptionTyping or using Jest's test/it syntax with a descriptive title.

function gh15479() {

[hasezoey]

LGTM, works with typegoose in its current state. Though because it modifies something likely used, i would agree to postpone it to a minor release.