add step_context

lib/memex/steps/step_context.ex

@@ -0,0 +1,21 @@
+defmodule Memex.Steps.StepContext do
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  @primary_key {:id, :binary_id, autogenerate: true}
+  @foreign_key_type :binary_id
+  schema "step_contexts" do
+
+    field :step_id, :binary_id
+    field :context_id, :binary_id
+
+    timestamps()
+  end
+
+  @doc false
+  def changeset(step_context, attrs) do
+    step_context
+    |> cast(attrs, [])
+    |> validate_required([])
+  end
+end