Support structured logging

[hejfelix]

Currently, the org.legogroup.Output expects String as input which would stop the application from efficiently doing any kind of structured logging.
Combining the Printer and Output concept would easily solve this with a method signature similar to:

  def output(
      epochMillis: EpochMillis,
      level: LogLevel,
      info: LogInfo,
      message: String,
      context: List[(String, String)],
  ): F[Unit]

however, this will lead to a less composable architecture. We could change the arguments to a case class:

case class LogLine(      
      epochMillis: EpochMillis,
      level: LogLevel,
      info: LogInfo,
      message: String,
      context: List[(String, String)],
      )

which would make it much easier to pass around. I still think there's some merit to separating the stateless transformations from the effectful outputs, but it's not easy to pick a suitable input type for the Output class methods.

Consider the following:

• The user wants to print human readable lines in color to the std output
• The user also wants to send structured output as json to a structured log server via the network

Here, it would be nice to allow pairing up printers and outputs which would basically solve this and many more cases.

On a final note, I do realize that we could simply change it to be 1 concept of LogLine => F[Unit] and let the library users do their own function composition, but I feel like that may be a bit too unclear and not very intention-revealing. This solution will not force people to use String as an intermediate format, though!

Thoughts are very welcome!

[hejfelix]

Solved with #65

Closing.