HOCON supports combining conf files with fallbacks, which means if a value is not defined in resource-a.conf,
but is defined in resource-b.conf, then ConfigFactory.load("resource-a").withFallback(ConfigFactory.load("resource-b"))
will contain values from both resource files. For any variable in both, that variable will be populated by resource-a.conf.
Additionally, we can provide environment variables to populate the resource
file by defining db.sam_read.user=${?SAM_READ_USER}, which will only load the value if the environment variable is defined.
With this, we can define an env.conf, filled with optional environment variables, and load that with the default config
as a fallback, meaning environment variables that are defined will be read, and those that aren't will be populated by
the default conf file.