Smart templates for SAML-messages + metadata

[tvdijen]

At this point we have some XML-metadata files that are useful for testing.
However, when it comes to SAML messages, we have to deal with token lifetime etc.
To create theses messages with several options, perhaps some form of corruption, signed / unsigned, we have to think of a way to dynamically create them for use in our tests..
My idea here is to work with Twig-templates that can be loaded / configured / processed by a class, but perhaps someone else has a better idea..