Update core-services.md

[mocsa]

For drafts-enabled applications we may need to use the drafts entity.

[renejeglinsky]

Hi @mocsa ,
thanks a lot for your contribution. How to do this with draft, is explained in the Fiori Support guide. Have you seen that? Usually we try to avoid duplications. Maybe sth like "For draft see ..." would be an option?
@johannes-vogel What do you think about adding this sentence here?

[johannes-vogel]

a link would be ok, I think