Add a module to be use'd to define entrypoints

Author: tompave

lib/fun_with_flags/entry_point.ex

@@ -0,0 +1,31 @@
+defmodule FunWithFlags.EntryPoint do
+  @moduledoc """
+  Defines an entry point to query feature flags.
+
+  ## Example
+
+      defmodule MyApp.Flags do
+        use FunWithFlags.EntryPoint
+      end
+
+      MyApp.Flags.enabled?(:foo)
+
+  """
+
+  @doc false
+  defmacro __using__(opts) do
+    quote bind_quoted: [opts: opts] do
+      @behaviour FunWithFlags.EntryPoint
+
+      # TODO: add what's currently in the top module.
+    end
+  end
+
+  @doc """
+  An entry point must define this callback to provide its configuration.
+
+  This function is supposed to retrieve any runtime config (e.g. ENV vars) and
+  return it as a keyword list.
+  """
+  @callback config() :: {:ok, Keyword.t()}
+end