Rails 8_1 Compatibility

[simps614]

Fixes #1479

Rails 8.1 changed ActionDispatch::Routing::Mapper::Resources::Resource#initialize to require keyword args (only:, except:, **options). The JSONAPI‑Resources DSL still passes a positional options hash, so jsonapi_relationships never runs and relationship routes are missing.

Adding the ** operator to **options converts the hash into keyword args.

Tests that fail without this change: test/controllers/controller_test.rb

I ran into several other deprecations.

• ActiveSupport::Deprecation.silenced will not work the way it was set up in the tests because #silenced now works on an instance of Deprecators instead of globally. I created a module JSONAPI.deprecator so that the gem can use its own instance of Deprecator and the tests can work as designed.
• :unprocessable_entity was deprecated in favor of :unprocessable_content
• Used lazy method evaluation for Configuration because Rails 8.1 does not guarantee class-body initialization order, so @configuration was returning nil.
• My team uses an active_record oracle adapter. Oracle unquoted identifiers are automatically stored as UPPERCASE. Rails 8.1 no longer normalizes the case automatically for queries, so I added a condition for using the oracle adapter.
• length is no longer a valid column constraint. Used limit instead
• references: is not a valid option key for ActiveRecord migrations. Excplicitly pass a foreign_key to the things table instead.
• :none is not a valid active_record schema format in Rails 8.1
• Disabled foreign key constraints for SQLite tests
• Use ActiveRecord::Base.connection.quoted_true as it is database agnostic

There are a few warnings in the test suite that I did not address because they were unrelated to this change.

All Submissions:

• I've checked to ensure there aren't other open Pull Requests for the same update/change.
• I've submitted a ticket for my issue if one did not already exist.
• My submission passes all tests. (Please run the full test suite locally to cut down on noise from travis failures.)
• I've used Github auto-closing keywords in the commit message or the description.
• I've added/updated tests for this change.

### New Feature Submissions:

- [ ] I've submitted an issue that describes this feature, and received the go ahead from the maintainers.
- [ ] My submission includes new tests.
- [ ] My submission maintains compliance with JSON:API.

Bug fixes and Changes to Core Features:

• I've included an explanation of what the changes do and why I'd like you to include them.
• I've provided test(s) that fails without the change.

Reviewer Checklist:

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