Add logger to logical database backends

[tyrannosaurus-becks]

Unlike for regular auth and secret backends, database backends are not provided with a logger during their setup or as part of their interface. It would be great to provide the Vault logger to them. With Vault on Info level, I've been unable to gain any output from the following calls in a mounted database plugin:

hclog.Default().Info("setting username " + c.username)
fmt.Println("setting username " + c.username)
log.Print("setting username " + c.username)
q.Q("setting username " + c.username)

[meshantz]

This would be really handy.

I found a forum post that seems to apply to other plugins, but it provided me with a workaround for the moment:

If you set vault's log_level to "debug", you'll get any messages sent through your (unconfigured) hclog.Default() logger.

If anyone can advise on how to properly configure a logger to send logs back to the vault process - assuming it's possible - from a database plugin context, that would also be helpful until this is available.