Add GitHub Actions CI matrix

Run the spec suite across a matrix of Ruby, Rails, and ActiveAdmin
versions on every push and pull request.

Matrix:
- Ruby 3.2, 3.3, 3.4
- Rails 7.2.0, 8.0.0
- ActiveAdmin 3.4.0, 3.5.0

Wiring:

- Gemfile now resolves the rails/activeadmin versions from the RAILS
  and AA environment variables (defaulting to 7.2.0 / 3.5.0 for local
  dev), which lets a single Gemfile drive every matrix cell.
- spec/dummy/config/application.rb picks load_defaults dynamically
  based on the resolved Rails version so the dummy app boots cleanly
  under both 7.2 and 8.0.
- Gemspec Ruby floor dropped from 3.3 to 3.2 to match the matrix.
- Add a CI status badge to the README.

Modeled on activeadmin-plugins/active_admin_sidebar's workflow.

Author: Fivell

.github/workflows/ci.yml

@@ -0,0 +1,30 @@
+name: CI
+on:
+  pull_request:
+  push:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  test:
+    name: Ruby ${{ matrix.ruby }} / Rails ${{ matrix.rails }} / AA ${{ matrix.activeadmin }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        ruby: ['3.2', '3.3', '3.4']
+        rails: ['7.2.0', '8.0.0']
+        activeadmin: ['3.4.0', '3.5.0']
+    env:
+      RAILS: ${{ matrix.rails }}
+      AA: ${{ matrix.activeadmin }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: ${{ matrix.ruby }}
+          bundler-cache: true
+      - name: Run tests
+        run: bundle exec rspec spec

Gemfile

@@ -4,7 +4,12 @@ source "https://rubygems.org"
 
 gemspec
 
-# Pin Rails for the dev/test environment. The gemspec allows >= 7.2 at
-# runtime, but the dummy app and specs are validated against 7.2.
-gem "rails", "~> 7.2.0"
-gem "activerecord", "~> 7.2.0"
+default_rails_version       = "7.2.0"
+default_activeadmin_version = "3.5.0"
+
+rails_version       = ENV.fetch("RAILS", default_rails_version)
+activeadmin_version = ENV.fetch("AA",    default_activeadmin_version)
+
+gem "rails",        "~> #{rails_version}"
+gem "activerecord", "~> #{rails_version}"
+gem "activeadmin",  "~> #{activeadmin_version}"

README.md

@@ -1,5 +1,7 @@
 # activeadmin-oidc
 
+[![CI](https://github.com/activeadmin-plugins/activeadmin-oidc/actions/workflows/ci.yml/badge.svg)](https://github.com/activeadmin-plugins/activeadmin-oidc/actions/workflows/ci.yml)
+
 OpenID Connect single sign-on for [ActiveAdmin](https://activeadmin.info/).
 
 Plugs OIDC into ActiveAdmin's existing Devise stack: JIT user provisioning, an `on_login` hook for host-owned authorization, a login-button view override, and a one-shot install generator. The OIDC protocol layer (discovery, JWKS, token verification, PKCE, nonce, state) is delegated to [`omniauth_openid_connect`](https://github.com/omniauth/omniauth_openid_connect).

activeadmin-oidc.gemspec

@@ -16,7 +16,7 @@ Gem::Specification.new do |spec|
   spec.license  = "MIT"
   spec.homepage = "https://github.com/fedoronchuk/activeadmin-oidc"
 
-  spec.required_ruby_version = ">= 3.3.0"
+  spec.required_ruby_version = ">= 3.2.0"
 
   spec.files = Dir[
     "lib/**/*",

spec/dummy/config/application.rb

@@ -23,7 +23,10 @@
 
 module Dummy
   class Application < Rails::Application
-    config.load_defaults 7.2
+    # Pick the nearest Rails defaults for the Rails version that's
+    # currently resolved. The CI matrix exercises 7.2 and 8.0.
+    rails_gem_version = Gem::Version.new(Rails.version)
+    config.load_defaults(rails_gem_version >= Gem::Version.new("8.0") ? 8.0 : 7.2)
     config.eager_load = false
     config.root = File.expand_path("..", __dir__)