gist of code causing error in template

mycode

order supplies schema
--------------------------------------------------
defmodule Ostobuddy.Ostomy.OrderSupplies do
    use Ecto.Schema
    import Ecto.Changeset
    alias Ostobuddy.Ostomy.Order
    alias Ostobuddy.Ostomy.OrderSupplies 
  
    schema "order_supplies" do        
      field :user_id, :integer, null: false
      field :supply_id, :integer, null: false
      field :qty_ordered, :integer, null: false
      field :price, :decimal, null: false
      timestamps()
      belongs_to :order, Order 
    end
    

    @required_fields ~w(user_id supply_id qty_ordered price)a 
    @all_fields ~w(user_id supply_id qty_ordered price)a
    
    def changeset(%OrderSupplies{} = order_supplies, attrs) do
      order_supplies
      |> cast(attrs, @all_fields )
      |> validate_required(@required_fields)  
      |> check_user_owns_supplies
      |> validate_number(:user_id, greater_than: 0)
      |> validate_number(:supply_id, greater_than: 0)
      |> validate_number(:qty_ordered, greater_than: 0)
      |> validate_number(:price, greater_than: 0)      
    end

    defp check_user_owns_supplies(changeset) do
      user_id = get_field(changeset, :user_id)
      supply_id= get_field(changeset, :supply_id)
  
      if Ostobuddy.Ostomy.user_owns_supply?(user_id, supply_id) == nil do
        changeset = 
          add_error(changeset, :supply_id, "You cannot use a supply you do not own.")      
          |> put_change(:valid?, false)
        changeset
      else
        changeset       #no change...
      end      
    end  
  end
  
  
  ------ Query in repo -----------
  -- this function is called from controlloer OrderSupplies
  
  def list_ordersupplies(id) do                
        query = from o in OrderSupplies, 
                join: s in Supply, where: s.id == o.supply_id,                    
                select: [ o.id, s.product_name, o.supply_id, o.qty_ordered, o.price], 
                where: o.order_id == ^id, 
                order_by: [desc: o.inserted_at]                

        Repo.all(query)
    end
    
    
  ----- the view template -----------
  
  <div class="panel-body">
    <div class="table-responsive">
        <table class="table table-bordered table-hover table-striped">
                <thead>
                    <tr>
                        <th>Supply</th>                                        
                        <th>Qty Ordered<br/>
                        <th>Price</th>
                    </tr>
                </thead>
                <%= @orders_supplies %>
                <tbody>

                    <%= for order_supply <- @orders_supplies do %> 
                        <tr>
                            <td><%= order_supply.product_name %></td>
                            <td><%= order_supply.qty_ordered %></td>
                             <td><%=  Decimal.to_string(order_supply.price)  %></td>                            
                        </tr>
                    <% end %>
                </tbody>
        </table>
    </div>    
</div>

------- and this is the controller method that fetches ordersupplies -------


def index(conn, %{"id" => id}) do
        user = Guardian.Plug.current_resource(conn)
        orders_supplies = Ostomy.list_ordersupplies(id)
        render(conn, "index.html", orders_supplies: orders_supplies)    
    end