Remove WantAssertionsSigned

WantAssertionsSigned requires that asserting parties sign the
assertions. This does not reflect how Spring Security actually
behaves, creating behavior mismatches.

Closes gh-10844

Author: jzheaux

saml2/saml2-service-provider/src/main/java/org/springframework/security/saml2/provider/service/metadata/OpenSamlMetadataResolver.java

@@ -81,7 +81,6 @@ public String resolve(RelyingPartyRegistration relyingPartyRegistration) {
 	private SPSSODescriptor buildSpSsoDescriptor(RelyingPartyRegistration registration) {
 		SPSSODescriptor spSsoDescriptor = build(SPSSODescriptor.DEFAULT_ELEMENT_NAME);
 		spSsoDescriptor.addSupportedProtocol(SAMLConstants.SAML20P_NS);
-		spSsoDescriptor.setWantAssertionsSigned(true);
 		spSsoDescriptor.getKeyDescriptors()
 				.addAll(buildKeys(registration.getSigningX509Credentials(), UsageType.SIGNING));
 		spSsoDescriptor.getKeyDescriptors()

saml2/saml2-service-provider/src/test/java/org/springframework/security/saml2/provider/service/metadata/OpenSamlMetadataResolverTests.java

@@ -37,8 +37,7 @@ public void resolveWhenRelyingPartyThenMetadataMatches() {
 		OpenSamlMetadataResolver openSamlMetadataResolver = new OpenSamlMetadataResolver();
 		String metadata = openSamlMetadataResolver.resolve(relyingPartyRegistration);
 		assertThat(metadata).contains("<EntityDescriptor").contains("entityID=\"rp-entity-id\"")
-				.contains("WantAssertionsSigned=\"true\"").contains("<md:KeyDescriptor use=\"signing\">")
-				.contains("<md:KeyDescriptor use=\"encryption\">")
+				.contains("<md:KeyDescriptor use=\"signing\">").contains("<md:KeyDescriptor use=\"encryption\">")
 				.contains("<ds:X509Certificate>MIICgTCCAeoCCQCuVzyqFgMSyDANBgkqhkiG9w0BAQsFADCBhDELMAkGA1UEBh")
 				.contains("Binding=\"urn:oasis:names:tc:SAML:2.0:bindings:HTTP-Redirect\"")
 				.contains("Location=\"https://rp.example.org/acs\" index=\"1\"")
@@ -54,7 +53,7 @@ public void resolveWhenRelyingPartyNoCredentialsThenMetadataMatches() {
 		OpenSamlMetadataResolver openSamlMetadataResolver = new OpenSamlMetadataResolver();
 		String metadata = openSamlMetadataResolver.resolve(relyingPartyRegistration);
 		assertThat(metadata).contains("<EntityDescriptor").contains("entityID=\"rp-entity-id\"")
-				.contains("WantAssertionsSigned=\"true\"").doesNotContain("<md:KeyDescriptor use=\"signing\">")
+				.doesNotContain("<md:KeyDescriptor use=\"signing\">")
 				.doesNotContain("<md:KeyDescriptor use=\"encryption\">")
 				.contains("Binding=\"urn:oasis:names:tc:SAML:2.0:bindings:HTTP-POST\"")
 				.contains("Location=\"https://rp.example.org/acs\" index=\"1\"")