Configure server Docker container at runtime

[gregbrowndev]

Currently, the http4s server reads its config from the src/main/resources/application.conf file. This file will contain sensitive data, such as the database credentials, which shouldn't be checked into the source control.

One option is to use variable expansion to read the sensitive data from environment variables that can easily be set on the Docker container run command. However, this seems like a lot of duplicated effort. Can we instead read the application.conf file contents, e.g. in JSON format, from an environment variable?