implicit encode Ecto schema with Jason

model.ex

  # inside an ecto Schema, adding this: 
  
  defimpl Jason.Encoder, for: [__MODULE__] do
    def encode(struct, opts) do
      Enum.reduce(Map.from_struct(struct), %{}, fn
        ({k, %Ecto.Association.NotLoaded{}}, acc) -> acc
        ({k, v}, acc) -> Map.reject(acc, fn {k, v} -> k === :__meta__ end) |> Map.put(k, v)
      end)
      |> Jason.Encode.map(opts)
    end
  end

# suggestion from: https://elixirforum.com/t/how-to-encode-ecto-schema-with-jason-with-all-fields/17221/2  
# Notice: I leave it here for testing only. It might be better to use Phoenix view to EXPLICITLY render json.