Add jsonapi_include_toplevel_object adapter option

[nilsding]

Purpose

Sometimes, I have the need to include the JSON-API top level object while it's disabled in the config. This PR adds the functionality to include it on the fly using an option to the serializer:

 ActiveModelSerializers::SerializableResource.new(
  UserSerializer.new(obj),
  adapter:                         :json_api,
  jsonapi_include_toplevel_object: true
).as_json

Changes

Pass instance options to the ActiveModelSerializers::Adapter::JsonApi::Jsonapi model, and modify the include_object? method to use the value of the instance option :jsonapi_include_toplevel_object instead of the global config, if given.

Caveats

Related GitHub issues

Additional helpful information

[mention-bot]

@nilsding, thanks for your PR! By analyzing the history of the files in this pull request, we identified @bf4, @domitian and @groyoh to be potential reviewers.

[NullVoxPopuli]

@beauby do you have opinions on this?

[beauby]

I agree this should be overridable locally (and although it is weird that jsonapi_include_toplevel_object would be an option on the resource, since it is a property of the document, not of the primary resource, I don't see an other way to do it currently).

[bf4]

Idea is good, needs discussion of option name and distinction between turning on default via an option and passing in the jsonapi object in an option.

[bf4]

Should just be jsonapi_object, I think. (jsonapi can't be the key since render uses that

[bf4]

A question I have is what should be different between wanting to pass in your own jsonapi object vs. telling the adapter to include the default one?