DefaultCacheDurationSeconds ignored in CachingService instance methods

[r-bennett]

Describe the bug
DefaultCacheDurationSeconds is being ignored in some code paths. It only appears to be used in AppCacheExtensions e.g. extension

LazyCache/LazyCache/AppCacheExtensions.cs

Line 74 in e38695b

public static Task<T> GetOrAddAsync<T>(this IAppCache cache, string key, Func<Task<T>> addItemFactory)

but not in the almost equivalent instance method

LazyCache/LazyCache/CachingService.cs

Line 182 in 33d055c

public virtual Task<T> GetOrAddAsync<T>(string key, Func<ICacheEntry, Task<T>> addItemFactory)

To Reproduce

            var cache = new CachingService
            {
                DefaultCachePolicy = {DefaultCacheDurationSeconds = 1}
            };

            var res1 = await cache.GetOrAddAsync("foo", async x => DateTime.UtcNow.Second);

            // wait for the item to expire
            await Task.Delay(TimeSpan.FromSeconds(2));

            // same key
            var res2 = await cache.GetOrAddAsync("foo", async x => DateTime.UtcNow.Second);
            // new key
            var res3 = await cache.GetOrAddAsync("bar", async x => DateTime.UtcNow.Second);
            
            Console.WriteLine(res1);
            Console.WriteLine(res2);
            Console.WriteLine(res3);

Expected behavior
A new value generated for each call, with output e.g.

23
25
25

Actual behavior
Same value reused for "foo", with output e.g.

23
23
25

Framework and Platform

• OS: Windows 10
• Framework net5.0
• LazyCache Version 2.1.3

Additional context
Similar to the report in #121, although this isn't because of lazy eviction

[alastairtree]

Yeah I think the line

LazyCache/LazyCache/CachingService.cs

Line 184 in 33d055c

return GetOrAddAsync(key, addItemFactory, null);

which is currently

return GetOrAddAsync(key, addItemFactory, null);

should be

return cache.GetOrAddAsync(key, addItemFactory, cache.DefaultCachePolicy.BuildOptions());

Could you submit a failing test like your example and a PR to fix please?

[neozhu]

@alastairtree can you merge this PR#190 and update the version to support dotnet 7?