Birth dates, birthday reminders API, allow instance admins to require minimum age

Signed-off-by: marcin mikołajczak <git@mkljczk.pl>

priv/repo/migrations/29220116183110_add_birth_date_to_users.exs

@@ -0,0 +1,10 @@
+defmodule Pleroma.Repo.Migrations.AddBirthDateToUsers do
+  use Ecto.Migration
+
+  def change do
+    alter table(:users) do
+      add_if_not_exists(:birth_date, :date)
+      add_if_not_exists(:hide_birth_date, :boolean, default: false, null: false)
+    end
+  end
+end