Changing VerificationContent interface method to return certificate by pointer

[haydentherapper]

Description

HasCertificate returns a certificate by value along with a boolean to denote if the certificate was returned. A proposed simplification of this interface would be to change it to Certificate() (*x509.Certificate), which has two benefits: Passing by pointer over copy to avoid copying potentially large certificates, and removing the need to return a boolean when you can simply check if the return value is not nil.

One question for the original implementers: Was this function named to mirror the other function that returns an interface and boolean, since we can't return an interface by pointer?

[steiza]

One question for the original implementers: Was this function named to mirror the other function that returns an interface and boolean, since we can't return an interface by pointer?

I think so, along with things like HasInclusionPromise() and HasInclusionProof() where we just return a bool. But I don't think we depend on this naming / consistency, and this proposed change sound fine to me.