Question: ETag support

[yubing24]

Do you consider supporting ETag and embed ETag value to the response header?

I know ETag calculation varies, so I would propose an interface function that accepts an entity (User or Group), and returns a string as ETag:

type IEtagCalculator interface {
    CalculateEtag(entity {}interface) string
}

This interface can be added to scim.ServerOption or scim.ServerArgs. This should allow supporting calculating ETag with one specific function

Client code will need to implement the ETag function. If not, the server should warn that ETag function is nil.

If you don't have plan to support ETag, would you be open to adding a SupportEtag field to ServiceProviderConfig so that the service configuration for ETag can be customized by client code?