Ensure binding is always 0.0.0.0.

Binds the server to all IP addresses of the container, so it can be accessed from outside the container.

railties/lib/rails/generators/rails/devcontainer/templates/devcontainer/Dockerfile.tt

@@ -1,3 +1,7 @@
 # Make sure RUBY_VERSION matches the Ruby version in .ruby-version
 ARG RUBY_VERSION=<%= Gem.ruby_version %>
 FROM ghcr.io/rails/devcontainer/images/ruby:$RUBY_VERSION
+
+# Ensure binding is always 0.0.0.0
+# Binds the server to all IP addresses of the container, so it can be accessed from outside the container.
+ENV BINDING="0.0.0.0"

railties/test/generators/app_generator_test.rb

@@ -1320,6 +1320,7 @@ def test_devcontainer
     end
     assert_file(".devcontainer/Dockerfile") do |content|
       assert_match(/ARG RUBY_VERSION=#{RUBY_VERSION}/, content)
+      assert_match(/ENV BINDING="0.0.0.0"/, content)
     end
     assert_file("test/application_system_test_case.rb") do |content|
       assert_match(/^    served_by host: "rails-app", port: ENV\["CAPYBARA_SERVER_PORT"\]/, content)

railties/test/generators/devcontainer_generator_test.rb

@@ -346,6 +346,7 @@ def test_system_test_option_skip
         def test_common_config
           assert_file(".devcontainer/Dockerfile") do |dockerfile|
             assert_match(/ARG RUBY_VERSION=#{RUBY_VERSION}/, dockerfile)
+            assert_match(/ENV BINDING="0.0.0.0"/, dockerfile)
           end
 
           assert_devcontainer_json_file do |devcontainer_json|