Add recognized activity types to a constant and use it in the test

lib/pleroma/constants.ex

@@ -85,6 +85,24 @@ defmodule Pleroma.Constants do
     ]
   )
 
+  const(activity_types,
+    do: [
+      "Create",
+      "Update",
+      "Delete",
+      "Follow",
+      "Accept",
+      "Reject",
+      "Add",
+      "Remove",
+      "Like",
+      "Announce",
+      "Undo",
+      "Flag",
+      "EmojiReact"
+    ]
+  )
+
   const(allowed_activity_types_from_strangers,
     do: [
       "Block",

test/pleroma/web/activity_pub/activity_pub_controller_test.exs

@@ -689,7 +689,9 @@ defmodule Pleroma.Web.ActivityPub.ActivityPubControllerTest do
     # Once we begin processing it through Oban we risk fetching the actor to validate the
     # activity which just leads to inserting a new user to process a Delete not relevant to us.
     test "Activities of certain types from an unknown actor are discarded", %{conn: conn} do
-      example_bad_types = ["Announce", "Delete", "Undo"]
+      example_bad_types =
+        Pleroma.Constants.activity_types() --
+          Pleroma.Constants.allowed_activity_types_from_strangers()
 
       Enum.each(example_bad_types, fn bad_type ->
         params =