improvement: add Ash.Igniter.codegen/2

lib/ash/igniter.ex

@@ -1,5 +1,32 @@
 defmodule Ash.Igniter do
-  @moduledoc false
+  @moduledoc "Codemods and utilities for working with Ash & Igniter"
+
+  @doc "Adds a codegen task, or updates the name to be `<old_name>_and_name`"
+  def codegen(igniter, name) do
+    has_codegen? =
+      Enum.any?(igniter.tasks, fn
+        {"ash.codegen", _args} ->
+          true
+
+        _ ->
+          false
+      end)
+
+    if has_codegen? do
+      Map.update!(igniter, :tasks, fn tasks ->
+        Enum.map(tasks, fn
+          {"ash.codegen", [old_name | rest]} ->
+            {"ash.codegen", [old_name <> "_and_#{name}" | rest]}
+
+          task ->
+            task
+        end)
+      end)
+    else
+      Igniter.add_task(igniter, "ash.codegen", [name])
+    end
+  end
+
   def csv_option(options, key, modifier \\ & &1) do
     Keyword.update(
       options,