Modified the saml parser to handle boolean attribute value types

[KEYCLOAK-4020]

saml-core/src/main/java/org/keycloak/saml/processing/core/parsers/util/SAMLParserUtil.java

@@ -320,6 +320,8 @@ public class SAMLParserUtil {
             return StaxParserUtil.getElementText(xmlEventReader);
         } else if(typeValue.contains(":base64Binary")){
             return StaxParserUtil.getElementText(xmlEventReader);
+        } else if(typeValue.contains(":boolean")){
+            return StaxParserUtil.getElementText(xmlEventReader);
         }