Arvados

Review comments:

1. How about the method name "has_symbols?" instead of "has_any_symbols?"

2. convert_serialized_symbols_to_strings method

This method checks "if attr.object_class == Hash"
Even though we have used only Hash type objects for serialized attributes, can't I have an array defined as seriazed attribute? For ex: "serialize :my_attr, Array"
Should this method hence also support Array objects as well? What if I said "serialize :my_attr, String" or some other db supported object?
Should this method intead omit this check and invoke "if self.class.has_any_symbols? attributes[colname]" for all cases or all supported cases?

3. Please add the below additional tests to ArvadosModelTest -> test "refuse symbol keys in serialized attribute: #{x.inspect}"

--- a/services/api/test/unit/arvados_model_test.rb
+++ b/services/api/test/unit/arvados_model_test.rb
@ -32,6 +32,12 @ class ArvadosModelTest < ActiveSupport::TestCase

[ {:a => 'foo'},
+    {'a' => :foo},
+    {:a => ['foo', 'bar']},
+    {'a' => [:foo, 'bar']},
+    {:a => [:foo, :bar]},
+    {:a => {'foo' => {'bar' => 'baz'}}},
+    {'a' => {:foo => {'bar' => 'baz'}}},
  {'a' => {'foo' => {:bar => 'baz'}}},
  {'a' => {'foo' => {'bar' => :baz}}},

Now at 15cc0bc

• Renamed to has_symbols?
• Commented convert_serialized_symbols_to_strings
• Convert all serialized types in convert_serialized_symbols_to_strings, not just Hash
• Added test cases as suggested
• Improved readability of has_symbols?