Add more metadata elements

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

lib/service/metadata/post.ex

@@ -1,9 +1,12 @@
 defimpl Mobilizon.Service.Metadata, for: Mobilizon.Posts.Post do
   alias Phoenix.HTML
   alias Phoenix.HTML.Tag
+  alias Mobilizon.Actors.Actor
   alias Mobilizon.Medias.{File, Media}
   alias Mobilizon.Posts.Post
+  alias Mobilizon.Web.Endpoint
   alias Mobilizon.Web.JsonLD.ObjectView
+  alias Mobilizon.Web.Router.Helpers, as: Routes
   import Mobilizon.Service.Metadata.Utils, only: [process_description: 2, strip_tags: 1]
 
   def build_tags(%Post{} = post, locale \\ "en") do
@@ -21,9 +24,35 @@ defimpl Mobilizon.Service.Metadata, for: Mobilizon.Posts.Post do
       ]
       |> maybe_add_post_picture(post)
 
+    breadcrumbs = %{
+      "@context" => "https://schema.org",
+      "@type" => "BreadcrumbList",
+      "itemListElement" => [
+        %{
+          "@type" => "ListItem",
+          "position" => 1,
+          "name" => Actor.display_name(post.attributed_to),
+          "item" =>
+            Endpoint
+            |> Routes.page_url(
+              :actor,
+              Actor.preferred_username_and_domain(post.attributed_to)
+            )
+            |> URI.decode()
+        },
+        %{
+          "@type" => "ListItem",
+          "position" => 2,
+          "name" => post.title
+        }
+      ]
+    }
+
     tags ++
       [
         Tag.tag(:meta, property: "twitter:card", content: "summary_large_image"),
+        ~s{<script type="application/ld+json">#{Jason.encode!(breadcrumbs)}</script>}
+        |> HTML.raw(),
         ~s{<script type="application/ld+json">#{json(post)}</script>} |> HTML.raw()
       ]
   end