add contexts

lib/memex/contexts/context.ex

@@ -0,0 +1,22 @@
+defmodule Memex.Contexts.Context do
+  use Ecto.Schema
+  import Ecto.Changeset
+
+  @primary_key {:id, :binary_id, autogenerate: true}
+  @foreign_key_type :binary_id
+  schema "contexts" do
+    field :content, :string
+    field :tag, {:array, :string}
+    field :title, :string
+    field :visibility, Ecto.Enum, values: [:public, :private, :unlisted]
+
+    timestamps()
+  end
+
+  @doc false
+  def changeset(context, attrs) do
+    context
+    |> cast(attrs, [:title, :content, :tag, :visibility])
+    |> validate_required([:title, :content, :tag, :visibility])
+  end
+end