Add Rails 8.1 to CI test matrix

- Add gemfiles/rails_8_1.gemfile with Rails 8.1 dependency
- Include rails_8_1.gemfile in test workflow matrix
- Add exclusions for incompatible Ruby/Rails combinations:
  - Ruby 3.0 excluded from Rails 8.1 tests
  - Ruby 3.1 excluded from Rails 8.0 tests (duplicate removal)
  - Ruby 3.1 excluded from rails_edge tests in edge workflow

Author: ericproulx

.github/workflows/edge.yml

@@ -11,6 +11,8 @@ jobs:
         exclude:
           - ruby: '3.0'
             gemfile: rails_edge
+          - ruby: '3.1'
+            gemfile: rails_edge
     runs-on: ubuntu-latest
     continue-on-error: true
     env:

.github/workflows/test.yml

@@ -24,7 +24,7 @@ jobs:
       fail-fast: false
       matrix:
         ruby: ['3.0', '3.1', '3.2', '3.3', '3.4']
-        gemfile: [Gemfile, gemfiles/rack_2_0.gemfile, gemfiles/rack_3_0.gemfile, gemfiles/rack_3_1.gemfile, gemfiles/rack_3_2.gemfile, gemfiles/rails_7_0.gemfile, gemfiles/rails_7_1.gemfile, gemfiles/rails_7_2.gemfile, gemfiles/rails_8_0.gemfile]
+        gemfile: [Gemfile, gemfiles/rack_2_0.gemfile, gemfiles/rack_3_0.gemfile, gemfiles/rack_3_1.gemfile, gemfiles/rack_3_2.gemfile, gemfiles/rails_7_0.gemfile, gemfiles/rails_7_1.gemfile, gemfiles/rails_7_2.gemfile, gemfiles/rails_8_0.gemfile, gemfiles/rails_8_1.gemfile]
         specs: ['spec --exclude-pattern=spec/integration/**/*_spec.rb']
         include:
           - ruby: '3.3'
@@ -53,8 +53,12 @@ jobs:
             gemfile: gemfiles/rails_7_2.gemfile
           - ruby: '3.0'
             gemfile: gemfiles/rails_8_0.gemfile
+          - ruby: '3.0'
+            gemfile: gemfiles/rails_8_1.gemfile
           - ruby: '3.1'
             gemfile: gemfiles/rails_8_0.gemfile
+          - ruby: '3.1'
+            gemfile: gemfiles/rails_8_1.gemfile
     runs-on: ubuntu-latest
     env:
       BUNDLE_GEMFILE: ${{ github.workspace }}/${{ matrix.gemfile }}

gemfiles/rails_8_1.gemfile

@@ -0,0 +1,6 @@
+# frozen_string_literal: true
+
+eval_gemfile '../Gemfile'
+
+gem 'rails', '~> 8.1'
+gem 'tzinfo-data', require: false