@JsonProperty(PROP_NAME_COMMON_DB_DETAILS)
    @JsonPropertyDescription("Defines a set of common database connection details to use if no connection details " +
                             "are defined for a service area in stroom, e.g. core or config. This means you can " +
                             "have all service areas running in a single database, have each in their own " +
                             "database or a mixture.")
    public CommonDbConfig getCommonDbConfig() {
        return commonDbConfig;
    }
Will construct a full immutable AppConfig tree will ALL defaults set.
stroom-config/stroom-config-app/src/main/java/stroom/config/app/AppConfig.java