[day-04] add training schema

With this we can represent a traning program for a user.

lib/wabanex/trainings/create.ex

@@ -0,0 +1,9 @@
+defmodule Wabanex.Trainings.Create do
+  alias Wabanex.{Training, Repo}
+
+  def call(params) do
+    params
+    |> Training.changeset()
+    |> Repo.insert()
+  end
+end