feat(user): add ecto migration for user

Signed-off-by: supercmmetry <vishaals2000@gmail.com>

priv/repo/migrations/20210809085801_create_users.exs

@@ -0,0 +1,12 @@
+defmodule Ketbin.Repo.Migrations.CreateUsers do
+  use Ecto.Migration
+
+  def change do
+    create table(:users) do
+      add :firebase_id, :string
+
+      timestamps()
+    end
+
+  end
+end