[VC Security & Trust Document] Trust in "Identity of Presenter (Holder)" needs improvement

[Macke]

Imported from AB/Connect bitbucket: https://bitbucket.org/openid/connect/issues/2009

Original Reporter: danielfett

By David: https://bitbucket.org/openid/connect/pull-requests/468#comment-376398590

(Re 2nd sentence:) This is not the case in general. Rather it is that the verifier can determine that the holder is entitled to present the verifiable credentials in the VP (and has not obtained the VCs by nefarious means). The holder may in fact control the subject e.g. when a parent holds the passport of a child.

(Re last sentence:) or to holders who are entitled to hold the VCs about the subject e.g. the owner of a pet, when the VC is the vaccination certificate of the pet