Fixup INSTALL.md

- add a big fat warning
- Do not mentioned the deprecated docker setup anymore
- Fixup docker-compose production setup

Dockerfile.production

@@ -1,23 +1,16 @@
 FROM osem/base
 
-# We copy the Gemfiles into this intermediate build stage so it's checksum
-# changes and all the subsequent stages (a.k.a. the bundle install call below)
-# have to be rebuild. Otherwise, after the first build of this image,
-# docker would use it's cache for this and the following stages.
-COPY Gemfile /osem/
-COPY Gemfile.lock /osem/
-RUN chown -R osem /osem
-
 # Add our files
+COPY --chown=1000:1000 . /osem/
+
 USER osem
 WORKDIR /osem/
-COPY --chown=osem:osem . /osem/
 
 # Install our bundle
 RUN export NOKOGIRI_USE_SYSTEM_LIBRARIES=1; bundle install --jobs=3 --retry=3 --without test development
 
-# Configure OSEM
-RUN mv config/database.yml.example config/database.yml
+# Generate assets
+RUN export RAILS_ENV=production; bundle exec rake assets:clobber assets:precompile
 
 ENV RAILS_ENV=production