Add utility functions for objects and activities.

lib/pleroma/activity.ex

@@ -1,9 +1,21 @@
 defmodule Pleroma.Activity do
   use Ecto.Schema
+  alias Pleroma.{Repo, Activity}
+  import Ecto.Query
 
   schema "activities" do
     field :data, :map
 
     timestamps()
   end
+
+  def get_by_ap_id(ap_id) do
+    Repo.one(from activity in Activity,
+      where: fragment("? @> ?", activity.data, ^%{id: ap_id}))
+  end
+
+  def all_by_object_ap_id(ap_id) do
+    Repo.all(from activity in Activity,
+      where: fragment("? @> ?", activity.data, ^%{object: %{id: ap_id}}))
+  end
 end