Fix CI by pinning json gem below 3.0 (#992)

json just released 3.0.0, which drops support for the quirks_mode:
keyword. multi_json's json_gem adapter still passes that option by
default, and Grape transparently resolves its Grape::Json wrapper to
MultiJson whenever the gem is loaded in the process - so any spec
exercising JSON request parsing crashes with
"ArgumentError: unknown keyword: quirks_mode".

A fix for this already landed on multi_json's main branch but hasn't
been released as a gem yet, so pinning json < 3.0 is the only lever
available until multi_json cuts a new release. CI runs bundle update
with no lockfile pinning, which is why this surfaced now.

Author: numbata

CHANGELOG.md

@@ -8,6 +8,7 @@
 
 * [#986](https://github.com/ruby-grape/grape-swagger/pull/986): Read a route's tags through `route.tags` instead of `route.options`; a blank `tags:` (`nil` or `[]`) now means "not specified" and derives the tag from the path. See [UPGRADING](UPGRADING.md) - [@ericproulx](https://github.com/ericproulx).
 * [#988](https://github.com/ruby-grape/grape-swagger/pull/988): Fix CI by replacing single-statement `rubocop:disable`/`enable` pairs with `rubocop:disable-next`, per rubocop 1.90's new `Style/DirectiveScope` cop - [@numbata](https://github.com/numbata).
+* [#992](https://github.com/ruby-grape/grape-swagger/pull/992): Fix CI by pinning `json` to `< 3.0` in the Gemfile; `json` 3.0 dropped support for the `quirks_mode:` keyword that `multi_json`'s adapter still passes by default, breaking JSON request parsing wherever Grape resolves `Grape::Json` to `MultiJson` - [@numbata](https://github.com/numbata).
 * Your contribution here.
 
 ### 2.2.0 (2026-08-06)

Gemfile

@@ -29,6 +29,9 @@ group :development, :test do
   end
 
   gem 'cgi'
+  # multi_json's json_gem adapter still passes quirks_mode: true by default,
+  # a keyword json 3.0 dropped support for (https://github.com/intridea/multi_json/issues/163).
+  gem 'json', '< 3.0'
   gem 'multi_json'
   gem 'rack-cors'
   gem 'rack-test'