code: func (n *Network) PeerUserCert(p *Peer, user string) string {
  	org := n.Organization(p.Organization)
  	Expect(org).NotTo(BeNil())
  
  	return filepath.Join(
  		n.PeerUserMSPDir(p, user),
  		"signcerts",
  		fmt.Sprintf("%s@%s-cert.pem", user, org.Domain),
  	)
  }
docs: // PeerUserCert returns the path to the certificate for the specified user in
  // the peer organization.