IBlogPost porte IsPublished : le endpoint liste ne le lâche plus sur le wire

Le blog API (Yavsc.Blogs/Program.cs) sérialise en System.Text.Json
(.AddControllers() par défaut), et BlogApiController.GetBlogspot retourne
IEnumerable<IBlogPost>. STJ n'émet que les membres du type déclaré
(l'interface), donc IsPublished — qui n'était que sur les classes
concrètes BlogPost / BlogPostDto — était dropped du payload liste.
PostIt lisait alors IsPublished=false pour tout billet, y compris
publiés (cas prod /BlogSpot/Details/13).

Fix : déclarer IsPublished sur IBlogPost. BlogPost et BlogPostDto
l'implémentent déjà. Tests de wire-shape
(IBlogPostWireShapeTests) ajoutés pour verrouiller le contrat au
niveau du boundary.

Co-Authored-By: Claude Code <noreply@anthropic.com>

src/Yavsc.Blogs.Tests/IBlogPostWireShapeTests.cs

@@ -0,0 +1,87 @@
+using System.Text.Json;
+using Yavsc.Blogspot;
+using Yavsc.Models.Blog;
+
+namespace Yavsc.Blogs.Tests;
+
+/// <summary>
+/// Wire-shape tests pinning that <see cref="IBlogPost.IsPublished"/>
+/// is carried on the JSON the blog API list endpoint emits.
+///
+/// <para>The blog API host (<c>Yavsc.Blogs/Program.cs</c>) serialises
+/// with System.Text.Json (the <c>.AddControllers()</c> default — no
+/// <c>AddNewtonsoftJson</c>), and <c>BlogApiController.GetBlogspot</c>
+/// returns <c>IEnumerable&lt;IBlogPost&gt;</c>. System.Text.Json emits
+/// only the members of the <b>declared</b> type, so a property that
+/// exists solely on the concrete <c>BlogPost</c> entity is dropped from
+/// the payload. <c>IsPublished</c> used to be one such property: it was
+/// on <c>BlogPost</c> and <c>BlogPostDto</c> but not on
+/// <see cref="IBlogPost"/>, so the list response omitted it and PostIt
+/// read <c>IsPublished == false</c> for every post — including
+/// published ones.</para>
+///
+/// <para>These tests reproduce that serialisation path directly
+/// (declared type <c>IEnumerable&lt;IBlogPost&gt;</c> through
+/// <see cref="JsonSerializer.Serialize(object, Type)"/>) and assert
+/// <c>isPublished</c> survives the round trip. They live in
+/// <c>Yavsc.Blogs.Tests</c> — the assembly that owns the blog API
+/// contract — so a regression at the wire boundary is caught here,
+/// where it manifested in production (PostIt showing a published
+/// post's status as <c>false</c>).</para>
+/// </summary>
+public sealed class IBlogPostWireShapeTests
+{
+    private static readonly JsonSerializerOptions WebDefaults
+        = new(JsonSerializerDefaults.Web);
+
+    [Fact]
+    public void IsPublished_is_emitted_when_list_is_serialised_as_IEnumerable_IBlogPost()
+    {
+        var post = new BlogPost
+        {
+            Id = 13,
+            Title = "Published",
+            AuthorId = "alice",
+            Article = "x",
+        };
+        post.IsPublished = true;
+
+        // Declared type mirrors GetBlogspot's return: IEnumerable<IBlogPost>.
+        IEnumerable<IBlogPost> list = new List<BlogPost> { post };
+
+        // Serialize with the DECLARED type, the way ASP.NET Core's
+        // SystemTextJsonOutputFormatter hands context.ObjectType (the
+        // action return type) to JsonSerializer.Serialize.
+        var json = JsonSerializer.Serialize(list, typeof(IEnumerable<IBlogPost>),
+            WebDefaults);
+
+        using var doc = JsonDocument.Parse(json);
+        var element = doc.RootElement[0];
+        // Web defaults use camelCase, so the property is "isPublished".
+        Assert.True(element.TryGetProperty("isPublished", out var isPublished),
+            $"isPublished was dropped from the list payload. JSON: {json}");
+        Assert.True(isPublished.GetBoolean());
+    }
+
+    [Fact]
+    public void IsPublished_round_trips_through_BlogPostDto_on_the_client()
+    {
+        // The shape the client (PostIt) receives and deserialises with
+        // PropertyNameCaseInsensitive = true (cf. YavscApiClient).
+        var json = """
+        [{
+          "id": 13,
+          "title": "Published",
+          "article": "x",
+          "authorId": "alice",
+          "isPublished": true
+        }]
+        """;
+
+        var posts = JsonSerializer.Deserialize<List<BlogPostDto>>(json,
+            new JsonSerializerOptions { PropertyNameCaseInsensitive = true })!;
+
+        var post = Assert.Single(posts);
+        Assert.True(post.IsPublished);
+    }
+}