%{"email" => “e@e.com", "first_name" => “Abe",
"last_name" => “Sam", "password" => “foobar", "state_id" => "2"}

#Ecto.Changeset<action: nil,
changes: %{password: "foobar",
password_hash: “xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx."},
errors: [], data: #SomeApp.User<>, valid?: true>

def update(conn, %{"id" => id, "user" => user_params}) do
  user = Repo.get!(User, id)
  changeset =  User.changeset(user, user_params)
  case Repo.update(changeset) do

def changeset(model, params \ %{}) do
    model
    |> cast(params, [:email, :first_name, :last_name, :password])
    |> assoc_constraint(:state)
    |> validate_required([:email, :first_name, :last_name, :password])
    |> unique_constraint(:email)
    |> validate_length(:password, min: 4, max: 100)
    |> put_pass_hash()
  end

schema "users" do
    field :email, :string
    field :password,  :string, virtual: true
    field :password_hash, :string
    field :first_name, :string
    field :last_name, :string
    belongs_to :state, SomeApp.State

    timestamps()
  end

|> cast(params, [:email, :first_name, :last_name, :password])

|> cast(params, [:email, :first_name, :last_name, :password, :state_id])