contexts.ex

defmodule App.AccountCtx do
  alias __MODULE__.User
  alias Ecto.Multi
  
  def create_account(params) do
    user_changeset = User.changeset(%User{}, params)
    Multi.new()
    |> Multi.insert(:create_account_on_acc_ctx, user_changeset)
    |> Multi.run(:send_email, &App.Emailer.send_mail/1) # Logic to send e-mail
  end
end

defmodule App.SchoolsCtx do
  alias __MODULE__.User
  alias Ecto.Multi
  
  def create_account(params) do
    user_changeset = User.changeset(%User{}, params)
    
    Multi.insert(Multi.new(), :create_account_on_sch_ctx, user_changeset)
  end
end

defmodule App.SomeResolverModule do
  alias Ecto.Multi
  alias App.{Repo, SchoolsCtx, AccountsCtx}
  
  def resolve_acc_creation(params, _) do
    schools = SchoolsCtx.create_user(params)
    accounts = AccountsCtx.create_user(params)
    
    all_operations = Multi.append(schools, accounts)
    Repo.transaction(all_operations)
  end
end