Merge branch 'active-user-count' into 'develop'

Monthly Active Users

Closes #2332

See merge request pleroma/pleroma!3283

priv/repo/migrations/20210122151424_add_last_active_at_to_users.exs

@@ -0,0 +1,11 @@
+defmodule Pleroma.Repo.Migrations.AddLastActiveAtToUsers do
+  use Ecto.Migration
+
+  def change do
+    alter table(:users) do
+      add(:last_active_at, :naive_datetime)
+    end
+
+    create_if_not_exists(index(:users, [:last_active_at]))
+  end
+end