fix LocalCache#read_multi_entries

In cache stores prepending `LocalCache`, serialized `Entry`
instances are stored in `LocalCache::LocalStore`. This
speeds up hot key lookups without a network roundtrip in a
context of a single given request.

However, with these entries being stored in their serialized
form, `#read_multi_entries` returns them directly to cache
consumers.

Instead, we will now deserialize these entries first.

activesupport/lib/active_support/cache/strategy/local_cache.rb

@@ -123,6 +123,9 @@ module ActiveSupport
             return super unless local_cache
 
             local_entries = local_cache.read_multi_entries(keys)
+            local_entries.transform_values! do |payload|
+              deserialize_entry(payload).value
+            end
             missed_keys = keys - local_entries.keys
 
             if missed_keys.any?

activesupport/test/cache/behaviors/local_cache_behavior.rb

@@ -286,4 +286,13 @@ module LocalCacheBehavior
       assert_equal false, @cache.read(key)
     end
   end
+
+  def test_local_cache_should_deserialize_entries_on_multi_get
+    keys = Array.new(5) { SecureRandom.uuid }
+    values = keys.index_with(true)
+    @cache.with_local_cache do
+      assert @cache.write_multi(values)
+      assert_equal values, @cache.read_multi(*keys)
+    end
+  end
 end