Fix passing a hash with string keys when fabricating a variable

lib/gitlab/ci/variables/collection/item.rb

@@ -34,7 +34,7 @@ def to_runner_variable
           def self.fabricate(resource)
             case resource
             when Hash
-              self.new(resource)
+              self.new(resource.symbolize_keys)
             when ::HasVariable
               self.new(resource.to_runner_variable)
             when self

spec/lib/gitlab/ci/variables/collection/item_spec.rb

@@ -75,6 +75,14 @@
       expect(resource).to eq variable
     end
 
+    it 'supports using a hash with stringified values' do
+      variable = { 'key' => 'VARIABLE', 'value' => 'my value' }
+
+      resource = described_class.fabricate(variable)
+
+      expect(resource).to eq(key: 'VARIABLE', value: 'my value')
+    end
+
     it 'supports using an active record resource' do
       variable = create(:ci_variable, key: 'CI_VAR', value: '123')
       resource = described_class.fabricate(variable)