Upgraded Rails version.

.ruby-version

@@ -1 +1 @@
-2.6.7
+2.7.0

Dockerfile

@@ -2,6 +2,9 @@ FROM ruby:2.7.0
 
 LABEL maintainer="BarKeeper (Kai Müller, Sarah Wiechers)"
 
+RUN addgroup --gid 1000 barkeeper
+RUN adduser --disabled-password --gecos '' --uid 1000 --gid 1000 barkeeper
+
 ARG PUMA_PORT
 
 RUN apt-get update -qq && apt-get install -y build-essential libpq-dev nodejs cmake
@@ -10,10 +13,12 @@ ENV RAILS_ROOT /var/www/barkeeper
 RUN mkdir -p $RAILS_ROOT
 WORKDIR $RAILS_ROOT
 
-RUN gem install rails bundler
+ENV BUNDLER_VERSION=2.3.5
+RUN gem install rails bundler:2.3.5
 COPY Gemfile Gemfile
-COPY Gemfile.lock Gemfile.lock
+
 RUN bundle install
+RUN chown -R barkeeper:barkeeper $RAILS_ROOT
 
 RUN bundle exec rails assets:precompile
 EXPOSE $PUMA_PORT

Gemfile

@@ -4,7 +4,7 @@ source 'https://rubygems.org'
 
 ruby '2.7.0'
 
-gem 'rails', '5.2.4.6'
+gem 'rails', '5.2.7'
 
 # Postgres
 gem 'pg'
@@ -67,7 +67,7 @@ group :development do
   gem 'binding_of_caller' # Extends features of better_errors
   gem 'meta_request' # Supporting gem for Google Chrome Rails Panel
   gem 'licensed' # Check compatibility of gem licenses
-  gem 'spring' # Spring speeds up development by keeping your application running in the background
+  gem 'spring', '~> 3' # Spring speeds up development by keeping your application running in the background
   gem 'yard' # Documentation generation tool
 end