Add backend and endpoints for Feed Tokens

Closes #19 #86 #87

Signed-off-by: Thomas Citharel <tcit@tcit.fr>

priv/repo/migrations/20190307133518_feed_token_table.exs

@@ -0,0 +1,13 @@
+defmodule Mobilizon.Repo.Migrations.FeedTokenTable do
+  use Ecto.Migration
+
+  def change do
+    create table(:feed_token, primary_key: false) do
+      add(:token, :string, primary_key: true)
+      add(:actor_id, references(:actors, on_delete: :delete_all), null: true)
+      add(:user_id, references(:users, on_delete: :delete_all), null: false)
+
+      timestamps(updated_at: false)
+    end
+  end
+end