Add membership table

lib/architex/schema/membership.ex

@@ -0,0 +1,18 @@
+defmodule Architex.Membership do
+  use Ecto.Schema
+
+  alias Architex.{Account, Room}
+
+  @type t :: %__MODULE__{
+          account_id: integer(),
+          room_id: String.t(),
+          membership: String.t()
+        }
+
+  @primary_key false
+  schema "membership" do
+    belongs_to :account, Account, primary_key: true
+    belongs_to :room, Room, primary_key: true, type: :string
+    field :membership, :string
+  end
+end