Checkmk Werk 15445: SAML metadata endpoint: support HEAD requests

ID: 15445 Title: SAML metadata endpoint: support HEAD requests Component: setup Level: 1 Class: New feature Version: 2.3.0b1 Some identity providers (e.g. Net IQ) require the HTTP headers first in order to import the XML metadata. The Checkmk metadata endpoint for SAML now supports this request method.