Fix binary-id generator location in config/config.exs

Previously the config for the phoenix generators was appended to the
file. This is technically not a problem, however the comment for the
`import_config "#{Mix.env}.exs" explicitly states that it should be at
the bottom of the file.

Before:

    # Import environment specific config. This must remain at the bottom
    # of this file so it overrides the configuration defined above.
    import_config "#{Mix.env}.exs"

    # Configure phoenix generators
    config :phoenix, :generators,
      binary_id: true

After:

    # Configure phoenix generators
    config :phoenix, :generators,
      binary_id: true

    # Import environment specific config. This must remain at the bottom
    # of this file so it overrides the configuration defined above.
    import_config "#{Mix.env}.exs"

The spacing in the template is deliberate to ensure there is only a
single space between the blocks.

installer/lib/phoenix_new.ex

@@ -196,6 +196,18 @@ defmodule Mix.Tasks.Phoenix.New do
         :error -> adapter_config
       end
 
+
+    generator_config =
+      case get_generator_config(adapter_config) do
+        []               -> nil
+        generator_config ->
+          """
+
+          # Configure phoenix generators
+          config :phoenix, :generators#{kw_to_config(generator_config)}
+          """
+      end
+
     binding = [application_name: app,
                application_module: mod,
                phoenix_dep: phoenix_dep(phoenix_path),
@@ -214,6 +226,7 @@ defmodule Mix.Tasks.Phoenix.New do
                adapter_module: adapter_module,
                adapter_config: adapter_config,
                hex?: Code.ensure_loaded?(Hex),
+               generator_config: generator_config,
                namespaced?: Macro.camelize(app) != mod]
 
     copy_from path, binding, @new
@@ -274,21 +287,10 @@ defmodule Mix.Tasks.Phoenix.New do
         adapter: #{inspect binding[:adapter_module]}#{kw_to_config adapter_config[:prod]},
         pool_size: 20
       """
-
-      case generator_config(adapter_config) do
-        [] ->
-          :ok
-        generator_config ->
-          append_to path, "config/config.exs", """
-
-          # Configure phoenix generators
-          config :phoenix, :generators#{kw_to_config(generator_config)}
-          """
-      end
     end
   end
 
-  defp generator_config(adapter_config) do
+  defp get_generator_config(adapter_config) do
     adapter_config
     |> Keyword.take([:binary_id, :migration, :sample_binary_id])
     |> Enum.filter(fn {_, value} -> not is_nil(value) end)

installer/templates/new/config/config.exs

@@ -22,7 +22,7 @@ config :<%= application_name %>, <%= application_module %>.Endpoint,
 config :logger, :console,
   format: "$time $metadata[$level] $message\n",
   metadata: [:request_id]
-
+<%= generator_config %>
 # Import environment specific config. This must remain at the bottom
 # of this file so it overrides the configuration defined above.
 import_config "#{Mix.env}.exs"