<!-- From https://en.wikipedia.org/wiki/SAML_2.0#SP_Redirect_Request;_IdP_POST_Response -->
<samlp:AuthnRequest
  xmlns:samlp="urn:oasis:names:tc:SAML:2.0:protocol"
  xmlns:saml="urn:oasis:names:tc:SAML:2.0:assertion"
  ID="identifier_1"
  Version="2.0"
  IssueInstant="2004-12-05T09:21:59Z"
  AssertionConsumerServiceIndex="0">
  <saml:Issuer>https://sp.example.com/SAML2</saml:Issuer>
  <samlp:NameIDPolicy
    AllowCreate="true"
    Format="urn:oasis:names:tc:SAML:2.0:nameid-format:transient"/>
</samlp:AuthnRequest>