Store the client application data in ActivityStreams format

lib/pleroma/web/mastodon_api/controllers/status_controller.ex

@@ -423,7 +423,7 @@ def bookmarks(%{assigns: %{user: user}} = conn, params) do
   defp put_application(params, %{assigns: %{token: %Token{user: %User{} = user} = token}} = _conn) do
     if user.disclose_client do
       %{client_name: client_name, website: website} = Repo.preload(token, :app).app
-      Map.put(params, :application, %{name: client_name, website: website})
+      Map.put(params, :application, %{type: "Application", name: client_name, url: website})
     else
       Map.put(params, :application, nil)
     end

lib/pleroma/web/mastodon_api/views/status_view.ex

@@ -180,7 +180,7 @@ def render(
       media_attachments: reblogged[:media_attachments] || [],
       mentions: mentions,
       tags: reblogged[:tags] || [],
-      application: activity_object.data["application"] || nil,
+      application: build_application(activity_object.data["application"]),
       language: nil,
       emojis: [],
       pleroma: %{
@@ -345,7 +345,7 @@ def render("show.json", %{activity: %{data: %{"object" => _object}} = activity}
       poll: render(PollView, "show.json", object: object, for: opts[:for]),
       mentions: mentions,
       tags: build_tags(tags),
-      application: object.data["application"] || nil,
+      application: build_application(object.data["application"]),
       language: nil,
       emojis: build_emojis(object.data["emoji"]),
       pleroma: %{
@@ -534,4 +534,8 @@ defp build_emoji_map(emoji, users, current_user) do
       me: !!(current_user && current_user.ap_id in users)
     }
   end
+
+  @spec build_application(map() | nil) :: map() | nil
+  defp build_application(%{type: _type, name: name, url: url}), do: %{name: name, website: url}
+  defp build_application(_), do: nil
 end

test/pleroma/web/activity_pub/transmogrifier_test.exs

@@ -205,14 +205,17 @@ test "it strips internal fields" do
       {:ok, activity} =
         CommonAPI.post(user, %{
           status: "#2hu :firefox:",
-          application: %{name: "TestClient", website: "https://pleroma.social"}
+          application: %{type: "Application", name: "TestClient", url: "https://pleroma.social"}
         })
 
       # Ensure injected application data made it into the activity
       # as we don't have a Token to derive it from, otherwise it will
       # be nil and the test will pass
-      assert %{"application" => %{name: "TestClient", website: "https://pleroma.social"}} =
-               activity.object.data
+      assert %{
+               type: "Application",
+               name: "TestClient",
+               url: "https://pleroma.social"
+             } == activity.object.data["application"]
 
       {:ok, modified} = Transmogrifier.prepare_outgoing(activity.data)