Manually register the Twirl compiler toolchain

MODULE.bazel

@@ -22,6 +22,8 @@ register_toolchains(
     "//:repository_default_toolchain_21_definition",
     "//scala:zinc_2_13",
     "//scala:zinc_3",
+    "//twirl-toolchain:twirl-2-13",
+    "//twirl-toolchain:twirl-3",
 )
 
 # Please ensure these stay up-to-date with the versions in `versions.bzl`. Unfortunately,

twirl-toolchain/BUILD.bazel

@@ -1,8 +1,21 @@
 load("@bazel_skylib//:bzl_library.bzl", "bzl_library")
+load("@bazel_skylib//rules:common_settings.bzl", "string_flag", "string_setting")
 load(":create-toolchain.bzl", "create_twirl_toolchain")
 
 toolchain_type(name = "toolchain_type")
 
+string_setting(
+    name = "original-twirl-toolchain",
+    build_setting_default = "",
+    visibility = ["//visibility:public"],
+)
+
+string_flag(
+    name = "twirl-toolchain",
+    build_setting_default = "twirl-3",
+    visibility = ["//visibility:public"],
+)
+
 create_twirl_toolchain(
     name = "twirl-3",
     twirl_compiler = "//twirl-compiler-cli:twirl-compiler-cli-3",

twirl-toolchain/create-toolchain.bzl

@@ -12,7 +12,7 @@ def create_twirl_toolchain(name, twirl_compiler):
     native.config_setting(
         name = config_setting_name,
         flag_values = {
-            "@rules_twirl_toolchain//:twirl-toolchain": name,
+            "//twirl-toolchain": name,
         },
     )
 

twirl-toolchain/transitions.bzl

@@ -1,8 +1,8 @@
 # This approach of incoming transition, store original values, outgoing
 # transition, reset to original values is inspired by what the rules_go
 # folks are doing.
-toolchain_setting_key = "@rules_twirl_toolchain//:twirl-toolchain"
-original_toolchain_setting_key = "@rules_twirl_toolchain//:original-twirl-toolchain"
+toolchain_setting_key = "//twirl-toolchain"
+original_toolchain_setting_key = "//twirl-toolchain:original-twirl-toolchain"
 
 def _twirl_toolchain_transition_impl(settings, attr):
     """Update the rules_twirl toolchain to the overridden value. Store