Solve issue with SAML plugin 
… it is an issue with plug-in not with omniauth or ruby-saml gem/library (I will try document what I did, but basically it is a combination of insufficient and misleading documentation, and some weird programming solutions, without proper debugging, some comment is add, but without issues system is hard to understand way).
To stay with topic I suggest to do follow (according to my limited knowledge of Discourse and Ruby):
- manually edit container file (containers/app.yml)
- hint: if you like that container have different name you may change filename in containers directory and do all command on the way to change app to <your_name> (probably that is possible to do on some other way, but I didn’t have time to investigate)
- fork plugin in GitHub in your own space so you may manipulate with code, you may always call it in the same way like any other plugin from a container configuration file
- in many places you may add just
File.write('/var/www/discourse/log/production.log', 'Some text', mode: 'a')which will be written in log file everytime interpretation goes at that part of code - you may also fork Discourse project on GitHub and clon it from your place if you like to improve Discourse too