How to add a custom FluentD output plugin to Logging operator

If there is a FluentD plugin that the Logging operator does not support (for example, https://github.com/cloudfoundry-community/fluent-plugin-nats), here is how you can make it work with the Logging operator. Note that this is not a detailed tutorial, just a high-level overview of the process.

1. Add the plugin to the latest FluentD dockerfile used by the Logging operator for example, at the moment v1.11.
2. Write the Go code to have the Output CRD support the new plugin. You can use the Redis plugin pull request as an example.
3. Execute code and CRD generation by running make generate manifests To make sure the CI won’t complain, commit your changes and run make check-diff

For more details, see Developers.