Open Source required steps

[migue]

This pull request tries to complete all the steps required to release the library as an Open Source project. The different tasks that need to be performed are described in this issue.

Please, not that some of them do not apply to this project, like

• Create a Service Catalog entry

Since this is not a production system but a library that will be used by other people to build their final services.

Once this pull request is approved and merged, I will rewrite the history to have a single commit and will Open an issue in github/security-iam in order to make the repository public

[tgummerer]

One small nit inline that I think is worth fixing. Thanks for preparing this!

[migue]

I have pushed a set of changes, so we can run the linter in every pull and locally

The action is complaining:

pipe/pipeline.go:26:5: error-naming: error var FinishEarly should have name of the form ErrFoo (revive)
var FinishEarly = errors.New("finish stage early")

However, this variable annotation seems properly annotated:

// FinishEarly is an error that can be returned by a `Stage` to
// request that the iteration be ended early (possibly without reading
// all of its input). This "error" is considered a successful return,
// and is not reported to the caller.
//
//nolint:errname
var FinishEarly = errors.New("finish stage early")

Will take a look ...

[tgummerer]