Merge hash fields recursively for additional fields and child logger

[flexoid]

Hi.

First of all, thanks for a great gem!

When using structured logging, it is very common to have nested fields structure. Even some new standards, something like Elastic Common Schema completely relies on nested fields.

So it is very convenient to have a way to extend log events with additional fields and with child loggers, even if those fields are nested.

Something like this:

logger = Ougai::Logger.new(STDOUT)
logger.with_fields = { process: { pid: 123 } }

module_logger = logger.child(event: { module: "core" } })

class_logger = module_logger.child(event: { dataset: "core.archive" } })

class_logger.info("Item was archived successfully", event: { action: "item-archived" })

and expected:

{"msg": "Item was archived successfully", "process": { "pid": 123 }, "event": {"module": "core", "dataset": "core.archive", "action": "item-archived"} }

I don't think this change will cause any significant performance degradation. Hope it will be merged!

[flexoid]

Looks like codeclimate is offending on increased complexity, but in my opinion, it doesn't feel too complex, and any refactoring will only reduce performance. But let me know if you would prefer some refactoring to be done.

[tilfin]

I don't think it will have that much impact, but I will raise the major version because of the specification change.

[tilfin]

Thanks, LGTM!

[tilfin]

released at v2.0.0