fix ArgumentError building routes on Rails 8.1

[SAY-5]

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Bug fixes and Changes to Core Features:

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Test Plan:

rake test needs a database and currently errors out on a booted-app requirement in rails/test_help that's unrelated to this change (reproduces the same way on master with Rails 7.2 and 8.1, so it looks like a separate pre-existing gap in test_helper.rb's Rails 8 support). To verify this fix directly I installed actionpack 7.2.2.2 and 8.1.3.1 side by side and drew routes with jsonapi_resources through a real ActionDispatch::Routing::RouteSet#draw, which is what test/unit/routing_ext_test.rb does. That test errors with the exact ArgumentError: wrong number of arguments (given 4, expected 3) from the issue when run against master, and passes on both Rails versions with this change.

Reviewer Checklist:

• Maintains compliance with JSON:API
• Adequate test coverage exists to prevent regressions

Fixes #1488

Rails 8.1 changed ActionDispatch::Routing::Mapper::Resource#initialize (and SingletonResource) to take only:/except: as keywords instead of a trailing positional options hash (rails/rails#53689). jsonapi_resource(s) still calls both with a plain positional hash, so drawing any route on Rails 8.1 raises ArgumentError: wrong number of arguments (given 4, expected 3) before the app boots. Passing options with ** instead of positionally works on both the old and the new signature.

[kurko]

LGTM, but can you look at the failing test?

[SAY-5]

I checked the failed Ruby 2.7 / Rails 6.0.6 / PostgreSQL job. It ran 675 tests with 8,767 assertions and one failure: RequestTest#test_pagination_related_resources_data_includes, at the cache-warmup equality assertion in test_helper.rb:507 (seed 13850). The diff contains the same ten book_comments IDs in a different order inside the included book's relationship data.

Both that test and its helper are byte-identical between the PR head 96eef89 and base ca2eb53; the PR changes only the two routing constructor calls and their routing tests. The other 27 jobs passed. The base branch's corresponding job also passed, so these results do not establish that the failure is pre-existing or unrelated to this change.

I have not reproduced the failure with the matching Ruby/Rails/PostgreSQL setup, so the cause remains unverified. The next diagnostic is a base-versus-head run with seed 13850, tracing the relationship query ordering with and without caching. No assertion or test has been weakened, and no CI repair is claimed.