[day-02] add context to create/get a user

Create context module to create and fetch a user.

lib/wabanex/users/create.ex

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

lib/wabanex/users/get.ex

@@ -0,0 +1,20 @@
+defmodule Wabanex.Users.Get do
+  alias Wabanex.{Repo, User}
+
+  def call(id) do
+    id
+    |> Ecto.UUID.cast()
+    |> handle_result()
+  end
+
+  defp handle_result(:error), do: {:error, "Invalid id format"}
+
+  defp handle_result({:ok, uuid}) do
+    User
+    |> Repo.get(uuid)
+    |> case do
+      nil -> {:error, "User not found"}
+      user -> {:ok, user}
+    end
+  end
+end