Add support for asynchronous SLO profile

[tvdijen]

Closes #422

Support for this was requested in the simplesamlphp-repo

[monkeyiq]

I think that the aslo:Asynchronous should be in the samlp:LogoutRequest only. The spec seems fairly strong that the aslo:Asynchronous must be in the LogoutRequest in the specific Extensions nesting (sec 2.1).

[monkeyiq]

I was also looking a bit at the ssp code to see what might like to look at that subelement in order to not try a reply.

[tvdijen]

I think that the aslo:Asynchronous should be in the samlp:LogoutRequest only. The spec seems fairly strong that the aslo:Asynchronous must be in the LogoutRequest in the specific Extensions nesting (sec 2.1).

Yes, but the library should still accept anything in the samlp:Extensions. There could be extensions we don't support or recognize and that should not be a reason to reject the message. So the test in AuthnReqest is deliberately wrong (I should probably add a note)..

[monkeyiq]

While I was testing I added the following asserts in testMarshallingElementOrdering() to check if the Async element came back.

         $this->assertCount(6, $authnRequestElements);
         $this->assertEquals('samlp:Extensions', $authnRequestElements[0]->tagName);
+        $this->assertEquals(1,$authnRequestElements[0]->childElementCount);        
+        $childElement = $authnRequestElements[0]->firstElementChild;
+        $this->assertEquals($childElement->localName, 'Asynchronous');
         $this->assertEquals('saml:Subject', $authnRequestElements[1]->tagName);
         $this->assertEquals('samlp:NameIDPolicy', $authnRequestElements[2]->tagName);
         $this->assertEquals('saml:Conditions', $authnRequestElements[3]->tagName);

[monkeyiq]

I am happy to merge this. The two little things I found can be done before or after if desired.