Make it possible to run VAST without user configs

[dominiklohmann]

📔 Description

The new option --disable-default-config-dirs that may only be supplied on the command line disables the loading of user and system configuration, schema, and plugin directories. We use this option internally when generating VAST's man page and when running integration tests.

📝 Checklist

• All user-facing changes have changelog entries.
• The changes are reflected on docs.tenzir.com/vast, if necessary.
• The PR description contains instructions for the reviewer, if necessary.

🎯 Review Instructions

Commit-by-commit.

[lava]

Having the option makes sense and is desired, but the current behavior was a bit surprising for me:

$ cat config.yaml 
vast:
  endpoint: "localhost:6000"

$ ./bin/vast --disable-configuration --config=config.yaml start
[13:56:51.138] loaded configuration file: "config.yaml"
[13:56:51.265] VAST node is listening on localhost:6000

Also I'd intuitively expect the environment variables to be ignored as well with this, since they're just another channel to pass configuration.

Approval due to mis-click.

[dominiklohmann]

Also I'd intuitively expect the environment variables to be ignored as well with this, since they're just another channel to pass configuration.

The environment variables are just another workaround because of the same ordering issue we always have when loading plugins: Plugins can modify the command structure, and the command structure is required to parse the command line. Hence why the two variables must continue working, or we break integration tests for external plugins.

Similarly, --config still needs to work. Otherwise, the integration tests cannot run at all.

[lava]

Similarly, --config still needs to work. Otherwise, the integration tests cannot run at all.

Fine with me, but then we should adapt the option name & description accordingly. Currently the description says that it will also disable user configuration. Something like --disable-custom-directory-lookup?

[dominiklohmann]

I've reworded to --bare-mode per our discussion in Slack.

[lava]

Looking good now, module a few nits.

[dominiklohmann]

Renamed again to --disable-default-config-dirs after further discussion in Slack.