visibility: if litepub:directMessage is asserted, always report the object as "direct" visibility

lib/pleroma/web/activity_pub/visibility.ex

@@ -66,6 +66,9 @@ def get_visibility(object) do
       Enum.any?(to, &String.contains?(&1, "/followers")) ->
         "private"
 
+      object.data["directMessage"] == true ->
+        "direct"
+
       length(cc) > 0 ->
         "private"
 

test/web/activity_pub/visibilty_test.exs

@@ -117,4 +117,8 @@ test "get_visibility", %{
     assert Visibility.get_visibility(direct) == "direct"
     assert Visibility.get_visibility(unlisted) == "unlisted"
   end
+
+  test "get_visibility with directMessage flag" do
+    assert Visibility.get_visibility(%{data: %{"directMessage" => true}}) == "direct"
+  end
 end