it is changed in compile time

we can't change module attributes and endpoint settings in runtime

priv/repo/migrations/20190518032627_create_config.exs

@@ -0,0 +1,13 @@
+defmodule Pleroma.Repo.Migrations.CreateConfig do
+  use Ecto.Migration
+
+  def change do
+    create table(:config) do
+      add(:key, :string)
+      add(:value, :binary)
+      timestamps()
+    end
+
+    create(unique_index(:config, :key))
+  end
+end