new port: security/rubygem-omniauth-shibboleth

Ruby gem that implements an OmniAuth strategy for authenticating
through Shibboleth (SAML) for usage in rubygem-onmiauth.

WWW: https://github.com/toyokazu/omniauth-shibboleth

PR: 199753
Differential Revision: https://reviews.freebsd.org/D2507
Submitted by: Torsten Zuehlsdorff <ports@toco-domains.de>
Approved by: swills (mentor)