RubySaml::Utils::format_cert mishandles extra text outside of PEM block.

[netapp-mraymond]

RFC 7468 says "Data before the encapsulation boundaries are permitted" in a PEM format file. But the code in
https://github.com/onelogin/ruby-saml/blob/c38d72425b11aee5b2be595d44b407f8dfd92d6a/lib/onelogin/ruby-saml/utils.rb#L85
, when given a file with a single PEM block of certificate plus some non-ASCII extra text, will reformat in such way to move those extra text into the PEM block, resulting in downstream failures to decode.

[johnnyshields]

@netapp-mraymond if you'd like to change this, please make a PR with a new global config option which enforces the new way, something like OneLogin::RubySaml.strict_pem_format. Please add tests to ensure both the old and new way works. We'll deprecate the old way and flip the config to always be true in the next major version (3.x)