re-enable full CI matrix

Author: jamiemccarthy

.github/workflows/ci.yml

@@ -10,8 +10,24 @@ jobs:
       max-parallel: 2
       fail-fast: false
       matrix:
-        ruby-version: ['2.7.8']
+        ruby-version: ['2.6.10', '2.7.8', '3.0.6', '3.1.4', '3.2.2', '3.3.0']
         activerecord-version: ['5.2', '6.0', '6.1', '7.0', '7.1']
+        exclude:
+          # Rails 7's gemspec requires ruby >= 2.7
+          - ruby-version: '2.6.10'
+            activerecord-version: '7.0'
+          - ruby-version: '2.6.10'
+            activerecord-version: '7.1'
+          # Rails 5.x is unlikely ever to support ruby >= 3.0
+          # https://github.com/rails/rails/issues/40938#issuecomment-751569171
+          - ruby-version: '3.0.6'
+            activerecord-version: '5.2'
+          - ruby-version: '3.1.4'
+            activerecord-version: '5.2'
+          - ruby-version: '3.2.2'
+            activerecord-version: '5.2'
+          - ruby-version: '3.3.0'
+            activerecord-version: '5.2'
 
     steps:
     - name: Cleanup