Optional logging

[skovtunenko]

Hello!

Internally, the application is logging in plain text, like:

log.Printf("jobID=%v, jobname=%v, msg=starting", e.ID, j.Name)

This is not compatible with structured logging. It would be great if the logging could be abstracted using a logger interface so the users can use adapters and write logs in the format they want.

This is related to latest stable version v2.2.1

[skovtunenko]

Ideally, users shoud be able to inject their adapters for goflow logger interface via DI (dependency injection) upon constructing the Goflow instance.

For example, here is the generic logger interface that I'm using in my library:
https://github.com/skovtunenko/graterm/blob/main/logger.go

Here is how to inject the logger adapter (example):
https://github.com/skovtunenko/graterm/blob/main/terminator.go#L69-L80

In this case, the application will log only if the real logger was injected.