ActiveJob: fallback serializing String subclasses

https://github.com/rails/rails/pull/50090 broke serialization of String
subclasses that don't have serializers, like ActiveSupport::SafeBuffer.

Co-authored-by: John Hawthorn <john@hawthorn.email>

activejob/lib/active_job/arguments.rb

@@ -76,7 +76,11 @@ module ActiveJob
           if argument.class == String
             argument
           else
-            Serializers.serialize(argument)
+            begin
+              Serializers.serialize(argument)
+            rescue SerializationError
+              argument
+            end
           end
         when GlobalID::Identification
           convert_to_global_id_hash(argument)

activejob/test/cases/argument_serialization_test.rb

@@ -42,6 +42,9 @@ class ArgumentSerializationTest < ActiveSupport::TestCase
       end
   end
 
+  class StringWithoutSerializer < String
+  end
+
   setup do
     @person = Person.find("5")
   end
@@ -156,6 +159,14 @@ class ArgumentSerializationTest < ActiveSupport::TestCase
     ActiveJob::Serializers._additional_serializers = original_serializers
   end
 
+  test "serialize a String subclass object without a serializer" do
+    string_without_serializer = StringWithoutSerializer.new("foo")
+    serialized = ActiveJob::Arguments.serialize([string_without_serializer])
+    deserialized = ActiveJob::Arguments.deserialize(JSON.load(JSON.dump(serialized))).first
+    assert_instance_of String, deserialized
+    assert_equal string_without_serializer, deserialized
+  end
+
   test "serialize a hash" do
     symbol_key = { a: 1 }
     string_key = { "a" => 1 }