add touchless docker deploys

lib/cannery/release.ex

@@ -0,0 +1,20 @@
+defmodule Cannery.Release do
+  @app :cannery
+
+  def rollback(repo, version) do
+    load_app()
+    {:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :down, to: version))
+  end
+
+  defp load_app do
+    Application.load(@app)
+  end
+
+  def migrate do
+    load_app()
+
+    for repo <- Application.fetch_env!(@app, :ecto_repos) do
+      {:ok, _, _} = Ecto.Migrator.with_repo(repo, &Ecto.Migrator.run(&1, :up, all: true))
+    end
+  end
+end