Fix introspection of default input objects

[eapache]

It seems that the intent was to allow default input object values to be
specified in snake_case, but we weren't camelCasing them on output which
was leading to issues (in introspection and also schema printing).

See e.g. string_value which is actually the default for an argument stringValue (because graphql-ruby automatically camelCases argument names at definition time), in

graphql-ruby/spec/support/jazz.rb

Line 543 in 173ad1b

argument :arg_with_default, InspectableInput, required: false, default_value: { string_value: "S" }

Tweak an existing spec to cover this case (as well as the "enums
specifed as values not names" case), then add the missing call to
camelize.

@rmosolgo I'm not actually 100% sure if I'm interpreting the intention here properly. The code is obviously trivial/straightforward but maybe the intention was to force people to write their default values in camelCase and it's the Jazz schema that made a mistake?

This is a second stand-alone extraction from #3448.

cc @benjie

[rmosolgo]

You got the intention right -- I meant for the default_value: to look like the object that would get passed into resolvers: symbol, snake-cased keys and application values for enums.

[rmosolgo]

I'm trying to think, some people might've worked around this issue, will it "break" them if we fix it here? (I think that's ok, but I want to get it right in the changelog.)

[eapache]

🤔 I don't think it will break anything unless the user has disabled auto-camelization of argument names in general and is creating snake_case arguments in their actual schema? Otherwise writtenAsCamel default values should continue to pass through, and written_as_snake arguments will start working where they didn't before.

[rmosolgo]

Thanks for helping me think through that -- anyone who worked around this before should still be good to go 👍