By default, the Tunnelbroker looks for the config files in a `~/tunnelbroker/` directory. To add the ability to run the Tunnelbroker in Nix or any other environment we should add the ability to change the default directory for config files location.
This task introduces a few small related changes:
- Constants for the config files location were split into directory and file names for the production and sandbox configs.
- Add the ability to overwrite the config files directory by using of exported `TUNNELBROKER_CONFIG_FILE_DIRECTORY` environment variable in a `ConfigManager::load() method`.
Related Linear task: [[ https://linear.app/comm/issue/ENG-1589/update-the-config-file-location-to-run-tunnelbroker-in-nix | ENG-1589 ]]