Upgrade to Yarn 4, remove support for Node 16 (#27073)

.devcontainer/Dockerfile

@@ -4,7 +4,7 @@ FROM mcr.microsoft.com/devcontainers/ruby:1-3.2-bullseye
 # Install Rails
 # RUN gem install rails webdrivers
 
-ARG NODE_VERSION="16"
+ARG NODE_VERSION="20"
 RUN su vscode -c "source /usr/local/share/nvm/nvm.sh && nvm install ${NODE_VERSION} 2>&1"
 
 # [Optional] Uncomment this section to install additional OS packages.

.devcontainer/post-create.sh

@@ -11,7 +11,7 @@ bundle install
 git checkout -- Gemfile.lock
 
 # Fetch Javascript dependencies
-yarn --frozen-lockfile
+yarn install --immutable
 
 # [re]create, migrate, and seed the test database
 RAILS_ENV=test ./bin/rails db:setup