Inject patch in Docker Installation

I had a similar problem, but getting the GitLab oauth to work. I did the following:

volumes:
  - volume:
      host: /var/discourse/shared/standalone
      guest: /shared
  - volume:
      host: /var/discourse/shared/standalone/log/var-log
      guest: /var/log

## Plugins go here
## see https://meta.discourse.org/t/19157 for details
hooks:
  after_code:
    - exec:
        cd: $home/plugins
        cmd:
          - git clone https://github.com/discourse/docker_manager.git
          - git clone https://gitlab.com/gitlab-org/discourse-omniauth-gitlab.git
run:
  - exec: echo "Beginning of custom commands"
  ## If you want to set the 'From' email address for your first registration, uncomment and change:
  ## After getting the first signup email, re-comment the line. It only needs to run once.
  #- exec: rails r "SiteSetting.notification_email='info@unconfigured.discourse.org'"

  - exec: apt install unzip
  - exec: unzip /shared/ssl/NTAM_Collection_Ubuntu_2016.2.zip -d /usr/local/share/ca-certificates/
  - exec: chmod 444 /usr/local/share/ca-certificates/*
  - exec: c_rehash /usr/local/share/ca-certificates
  - exec: update-ca-certificates

  - exec: echo "End of custom commands"