Update gems to latest, upgrade Rails 7.1 to 8.1

.devcontainer/Dockerfile

@@ -1 +1,5 @@
-FROM mcr.microsoft.com/devcontainers/ruby:3.1
+FROM mcr.microsoft.com/devcontainers/ruby:3.3
+# Remove stale Yarn apt config baked into older base images — uses deprecated apt-key method
+# that Ubuntu 24.04 rejects, causing devcontainer feature installs (docker-in-docker) to fail.
+RUN rm -f /etc/apt/sources.list.d/yarn.list && \
+    apt-key del 62D54FD4003F6525 2>/dev/null || true

.devcontainer/devcontainer.json

@@ -5,7 +5,7 @@
   },
   "features": {
     "ghcr.io/devcontainers/features/node:latest": {},
-    "ghcr.io/devcontainers/features/docker-in-docker:latest": {},
+    "ghcr.io/devcontainers/features/docker-in-docker:latest": { "moby": false },
     "ghcr.io/devcontainers/features/sshd:latest": {}
   },
   "customizations": {

.github/workflows/test.yml

@@ -3,7 +3,7 @@ on: [push]
 jobs:
   image:
     name: Image
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v3
       - uses: docker/login-action@v2
@@ -18,7 +18,7 @@ jobs:
           cacheFrom: ghcr.io/rails-lambda/lamby-devcontainer
           runCmd: echo DONE!
   test:
-    runs-on: ubuntu-20.04
+    runs-on: ubuntu-24.04
     needs: image
     steps:
       - name: Checkout

Gemfile

@@ -2,9 +2,9 @@ source "https://rubygems.org"
 git_source(:github) {|repo_name| "https://github.com/#{repo_name}" }
 gemspec
 
-gem 'rails', '7.1.3.4'
-gem 'mocha', '~> 2.4'
-gem 'rack', "~> 3.1", ">= 3.1.7"
+gem 'rails', '~> 8.1'
+gem 'mocha', '~> 3.1'
+gem 'rack', "~> 3.2"
 
 group :test do
   gem 'lambdakiq'