Ruby 3 KwArgs: SAML SSOE (#11954)

Ruby 2.7 deprecated automatic casting of a hash passed as the last argument of a method to keyword arguments. You must now use actual keyword arguments (`foo(bar: 'baz')` instead of `foo({bar: 'baz'})`) or cast the hash to keyword args using the double splat (`foo(**{bar: 'baz'})`).

In preparation for upgrading to Ruby 3.0, we're implementing the new syntax for SAML error classes.

lib/saml/user_attributes/ssoe.rb

@@ -209,7 +209,7 @@ def validate!
         multiple_id_validations
         if should_raise_missing_uuid_error
           data = SAML::UserAttributeError::ERRORS[:uuid_missing].merge({ identifier: mhv_icn })
-          raise SAML::UserAttributeError, data
+          raise SAML::UserAttributeError.new(**data)
         end
       end