How Should I Get Application Configuration into my Docker Containers?
Eventhough this article was written in 2015, the configuration options stated for containers are still the same.
On the container level, options 1,2 and 4 are the only available options without using any external services.
For option 3, there are many key stores and services that can be used. But the idea is basically the same: Query a "service" and fetch the configuration during startup or runtime.