Merge branch 'fix/users_ap_id_not_null' into 'develop'

Ensure ap_id column in users table cannot be null

See merge request !2875

priv/repo/migrations/20200811143147_ap_id_not_null.exs

+defmodule Pleroma.Repo.Migrations.ApIdNotNull do
+  use Ecto.Migration
+
+  require Logger
+
+  def up do
+    Logger.warn(
+      "If this migration fails please open an issue at https://git.pleroma.social/pleroma/pleroma/-/issues/new \n"
+    )
+
+    alter table(:users) do
+      modify(:ap_id, :string, null: false)
+    end
+  end
+
+  def down do
+    :ok
+  end
+end