Add Rails 8.1.0.beta testing support

- Replace edge testing with Rails 8.1.0.beta in Appraisals
- Update CI workflow to test against Rails 8.1.0.beta
- Tests pass successfully with Rails 8.1.0.beta

Author: seuros

.github/workflows/ruby.yml

@@ -16,7 +16,7 @@ jobs:
         gemfiles:
           - gemfiles/active_model_7.2.gemfile
           - gemfiles/active_model_8.0.gemfile
-          - gemfiles/active_model_edge.gemfile
+          - gemfiles/active_model_8.1.gemfile
     env:
       BUNDLE_GEMFILE: ${{ github.workspace }}/${{ matrix.gemfiles }}
     steps:

Appraisals

@@ -9,6 +9,6 @@ appraise 'active_model_8.0' do
   gem 'activemodel', '~> 8.0.0'
 end
 
-appraise 'active_model_edge' do
-  gem 'activemodel', github: 'rails/rails', branch: 'main'
+appraise 'active_model_8.1' do
+  gem 'activemodel', '~> 8.1.0.beta'
 end

gemfiles/active_model_8.1.gemfile

@@ -0,0 +1,12 @@
+# This file was generated by Appraisal
+
+source "https://rubygems.org"
+
+gem "rubocop"
+gem "activemodel", "~> 8.1.0.beta"
+
+platforms :mri do
+  gem "debug"
+end
+
+gemspec path: "../"