Add Dockerisation and Collabora-specific patches

This does not include SSO yet.

Task: https://phabricator.apertis.org/T8044

Dockerfile.frontend-base

@@ -23,8 +23,8 @@ RUN apt-get update \
         npm \
         patch \
         pkgconf \
-        ruby \
-        ruby-dev \
+        ruby2.7 \
+        ruby2.7-dev \
         ruby-bundler \
         ruby-ffi \
         ruby-foreman \
@@ -45,7 +45,13 @@ RUN apt-get update \
 ADD src/api/Gemfile src/api/Gemfile.lock $INSTALLDIR/src/api/
 WORKDIR $INSTALLDIR/src/api/
 
-RUN sed -e '/BUNDLED WITH/,+1 d' Gemfile.lock > Gemfile.lock.new; \
+# Force Ruby 2.7 no matter what
+RUN for bin in $(dpkg -L ruby | grep /usr/bin/); do \
+      ln -sf ${bin}2.7 $bin; \
+    done
+RUN echo "ruby '~> 2.7.0'" >> Gemfile
+RUN sed -e '/BUNDLED WITH/,+1 d' Gemfile.lock \
+        -e 's/^  ruby$/  ruby '"$(ruby2.7 -v | cut -d' ' -f2)"'/' > Gemfile.lock.new; \
     diff -u Gemfile.lock Gemfile.lock.new; \
     mv Gemfile.lock.new Gemfile.lock