Add Rails 8.1 to CI matrix

Author: moritzhoeppner

.github/workflows/test.yml

@@ -8,7 +8,7 @@ jobs:
     strategy:
       matrix:
         ruby-version: ['3.1', '3.2', '3.3', '3.4']
-        rails-version: ['~> 7.2', '~> 8.0']
+        rails-version: ['~> 7.2', '~> 8.0', '~> 8.1']
         argon2-version: ['2.2', '2.3']
         orm:
           - adapter: active_record
@@ -17,8 +17,13 @@ jobs:
           - adapter: mongoid
             mongoid-version: 8.1.7
         exclude:
+          - rails-version: '~> 8.1'
+            ruby-version: '3.1'
           - rails-version: '~> 8.0'
             ruby-version: '3.1'
+          - orm:
+              adapter: mongoid
+            rails-version: '~> 8.1'
     env:
       RAILS_VERSION: ${{ matrix.rails-version  || '~> 8.0'}}
       MONGOID_VERSION: ${{ matrix.orm.mongoid-version || '8.1.6'}}