Do preserve the legacy API, but log a warning

lib/fun_with_flags.ex

@@ -7,10 +7,56 @@ defmodule FunWithFlags do
   See the [Usage](/fun_with_flags/readme.html#usage).
   """
 
-  use FunWithFlags.EntryPoint
+  defmodule PrivateEntryPoint do
+    @moduledoc false
+    use FunWithFlags.EntryPoint
 
-  @impl true
-  def config do
-    {:ok, []}
+    @impl true
+    def config do
+      {:ok, []}
+    end
+  end
+
+  require Logger
+  @deprecation_msg "Using the FunWithFlags module directly is deprecated. (TODO link to docs)"
+
+  def enabled?(flag_name, options \\ []) do
+    Logger.warning(@deprecation_msg)
+    PrivateEntryPoint.enabled?(flag_name, options)
+  end
+
+  def enable(flag_name, options \\ []) do
+    Logger.warning(@deprecation_msg)
+    PrivateEntryPoint.enable(flag_name, options)
+  end
+
+  def disable(flag_name, options \\ []) do
+    Logger.warning(@deprecation_msg)
+    PrivateEntryPoint.disable(flag_name, options)
+  end
+
+  def clear(flag_name, options \\ []) do
+    Logger.warning(@deprecation_msg)
+    PrivateEntryPoint.clear(flag_name, options)
+  end
+
+  def all_flag_names() do
+    Logger.warning(@deprecation_msg)
+    PrivateEntryPoint.all_flag_names()
+  end
+
+  def all_flags() do
+    Logger.warning(@deprecation_msg)
+    PrivateEntryPoint.all_flags()
+  end
+
+  def get_flag(flag_name) do
+    Logger.warning(@deprecation_msg)
+    PrivateEntryPoint.get_flag(flag_name)
+  end
+
+  def compiled_store() do
+    Logger.warning(@deprecation_msg)
+    PrivateEntryPoint.compiled_store()
   end
 end