function upsert_user_projects with put_assoc.ex

  def upsert_user_projects(user, project_ids) when is_list(project_ids) do
    projects =
      Project
      |> where([project], project.id in ^project_ids)
      |> Repo.all()

    with {:ok, _struct} <-
           user
           |> User.changeset_update_projects(projects)
           |> Repo.update() do
      {:ok, Accounts.get_user(user.id)}
    else
      error ->
        error
    end
  end