Incorrectly refactored in eb204573

Convert to our wrapper class for assertions

An issue in the code prevented the SameSite session cookie option from being set the first time we were reaching SSP when using PHP versions older than 7.3.

This fixes #1320

* fixed warning when Warning: session_create_id(): Failed to create new ID in /var/ssosp/lib/SimpleSAML/SessionHandlerPHP.php

* Use session_create_id() unconditionally

In master, we require PHP 7.2, which is guaranteed to provide `session_create_id()`. Therefore, we don't need the if clause any longer. Add also a warning when `session_create_id()` fails, and fall back gracefully to our old way to create session IDs.

Co-authored-by: Jaime Pérez Crespo <jaime.perez@uninett.no>

* Remove deprecated classes

* Remove support for certificate fingerprints

* Remove many deprecated methods and pieces of code

* Remove SAML1.1/Shib1.3 support

* Remove many superfluous annotations

* Update unit test to work with new PHPunit

Closes #1268 
Closes #1020 
Closes #431 
Closes #167 
Closes #151 

* Migrate assertions to Webmozart

Fixes #1270

PSR-12 compliancy

This (finally!) resolves #1176

This resolves #1176

Add support for RFC6265bis SameSite cookie attribute

Fixes for the remainder of lib/SimpleSAML

Fixes issue https://github.com/simplesamlphp/simplesamlphp/issues/793

When unserializing the session fails, the handler should return null instead of false. Additionally, SimpleSAML_Session::load() should make sure that it got an instance of SimpleSAML_Session, to avoid any misbehaving handlers to generate an issue.

This resolves #616.