First stable release of the silverstripe/saml module, which partially replaces the silverstripe/activedirectory module for SilverStripe 4.

Breaking API Changes:

Split silverstripe/activedirectory module into silverstripe/saml and silverstripe/ldap modules
Upgrade modules to support SilverStripe 4
Remove SAMLSecurityExtension and replace with configurable SAMLMiddleware to enforce SSO on all website requests
Stop SAMLAuthenticator::authenticate() from redirecting users to the IdP. This causes all kinds of issues (e.g. in cases where there are multiple authenticators)
Stop SAMLLoginHandler from extending LoginHandler, because it only deals with login
Move the SAML redirection from SAMLAuthenticator::authenticate() to SAMLHelper::redirect() so that it can be called by both SAMLLoginHandler and SAMLMiddleware

Non-breaking API Changes:

Update module to work as a vendormodule so it's not installed in web-root
Update onelogin/php-saml requirement to the latest v3.0.0 stable version which allows support for PHP 7.2 (no longer relies on the deprecated mcrypt PHP extension)

Add new authn_contexts array to allow developers to specify specific AuthN context classes that can be used for SSO. This helps when dealing with ADFS servers that enforce a specific ordering that places Password authentication ahead of windows, meaning that users are forced to login when reaching ADFS instead of being logged in automatically.

Completely re-write the SAMLController::acs() method so that it actually works, and gracefully handles SAML authentication errors
Ensure a Member is written to the DB, and use the new IdentityStore API to correctly log users in

Update documentation to remove references to AD sync (which is part of the silverstripe/ldap module)
Generally tidy up developer documentation