feat: add anonymize users task (#338)

* Anonimize users

* fix: suggestions

lib/mix/tasks/anonymize_users.ex

@@ -0,0 +1,45 @@
+defmodule Mix.Tasks.Anonymize.Users do
+  @moduledoc """
+  Task to anonymize users
+  """
+  use Mix.Task
+  import Ecto.Query, warn: false
+
+  alias Safira.Accounts.{Attendee, User}
+  alias Safira.Repo
+
+  def run(_args) do
+    Mix.Task.run("app.start")
+    users = Enum.shuffle(Repo.all(User))
+
+    for {user, index} <- Enum.with_index(users) do
+      anonymize_user(user, index + 1)
+    end
+  end
+
+  defp anonymize_user(%User{} = user, index) do
+    attendee =
+      Attendee
+      |> where([a], a.user_id == ^user.id)
+      |> Repo.one()
+
+    if not is_nil(attendee) do
+      attendee
+      |> Attendee.changeset(%{
+        name: "Attendee #{index}",
+        nickname: "attendee#{index}",
+        avatar: nil,
+        cv: nil
+      })
+      |> Repo.update!()
+    end
+
+    user
+    |> User.changeset(%{
+      email: "user#{index}@seium.org",
+      password: "password1234",
+      password_confirmation: "password1234"
+    })
+    |> Repo.update!()
+  end
+end