introduce importmaps

This commit introduces importmaps. They allow to use modern javacript ESM within rails without webpack, yarn etc.
see https://github.com/rails/importmap-rails for more details.

Co-authored-by: Philipp Rothmann <philipprothmann@posteo.de>
Co-authored-by: FGU <fgu@pragma-shift.net>

Gemfile

@@ -126,3 +126,5 @@ group :test do
   gem 'rswag-specs'
   gem 'hashie', '~> 3.4.6', require: false # https://github.com/westfieldlabs/apivore/issues/114
 end
+
+gem "importmap-rails", "~> 1.1"

Gemfile.lock

@@ -255,6 +255,9 @@ GEM
     i18n-spec (0.6.0)
       iso
     ice_cube (0.16.4)
+    importmap-rails (1.1.5)
+      actionpack (>= 6.0.0)
+      railties (>= 6.0.0)
     inherited_resources (1.13.1)
       actionpack (>= 5.2, < 7.1)
       has_scope (~> 0.6)
@@ -628,6 +631,7 @@ DEPENDENCIES
   i18n-js (~> 3.0.0.rc8)
   i18n-spec
   ice_cube
+  importmap-rails (~> 1.1)
   inherited_resources
   jquery-rails
   kaminari
@@ -686,4 +690,4 @@ DEPENDENCIES
   whenever
 
 BUNDLED WITH
-   2.4.3
+   2.4.5

app/javascript/application.js

@@ -0,0 +1 @@
+// Configure your import map in config/importmap.rb. Read more: https://github.com/rails/importmap-rails

app/views/layouts/_header.html.haml

@@ -8,10 +8,10 @@
     = csrf_meta_tags
     = stylesheet_link_tag "application", :media => "all"
     //%link(href="images/favicon.ico" rel="shortcut icon")
-
     = yield(:head)
     = foodcoop_css_tag
 
+
   %body
     = yield
 
@@ -19,7 +19,9 @@
       Javascripts
       \==================================================
     / Placed at the end of the document so the pages load faster
-    = javascript_include_tag "application"
+    = javascript_importmap_tags
+    = javascript_include_tag "application_legacy"
+
     :javascript
       I18n.defaultLocale = "#{I18n.default_locale}";
       I18n.locale = "#{I18n.locale}";

bin/importmap

@@ -0,0 +1,4 @@
+#!/usr/bin/env ruby
+
+require_relative "../config/application"
+require "importmap/commands"

config/importmap.rb

@@ -0,0 +1,2 @@
+# Pin npm packages by running ./bin/importmap
+pin "application", preload: true

config/initializers/assets.rb

@@ -9,4 +9,4 @@ Rails.application.config.assets.version = '1.0'
 # Precompile additional assets.
 # application.js, application.css, and all non-JS/CSS in the app/assets
 # folder are already added.
-# Rails.application.config.assets.precompile += %w( admin.js admin.css )
+Rails.application.config.assets.precompile += %w( application_legacy.js jquery.min.js )