Allow adding effect's contextual environment to the log context

[iRevive]

Closes #461. Some ideas are based on #676.

[iRevive]

The drawback of having this functionality in the core module.

I can move this code into log4cats-extras module. It could be handy if we want to provide some 'non-trivial' functionality: invocation positions (#525), etc.

[danicheg]

Just an idea, maybe it's worth creating a log4cats-mtl module then?

[iRevive]

Valid point

[iRevive]

I made log4cats-mtl module.

Should I set an upcoming release via tlVersionIntroduced := List("2.12", "2.13", "3").map(_ -> "2.7.0").toMap to suppress MiMa errors in the module? Or should I bump the base version instead: tlBaseVersion := 2.7?

[armanbilge]

If we are making a log4cats-mtl module, we should consider that cats-mtl may become a direct dependency of Cats Effect via typelevel/cats-effect#3385. Although that might be Cats Effect core only, and not the std module we're using here.

Just want to make sure that we think about the migration path in the case MTL ends up on the log4cats-core classpath (an acceptable migration path may be to accept the less-than-ideal situation as a historical artifact :)

[iRevive]

Is there any ETA? It would be nice to have Local as a part of cats-effect.

[armanbilge]

It could be as early as Cats Effect 3.6. I think last time that we discussed it Daniel was pretty convinced.